A abampere (aA) The unit of electric current in the CGSeniu system, defined as that current that, if flowing through two parallel conductors of negligible cross section and infinite length, placed 1 cm apart in vacuo, would produce on each conductor a force of 1 dyne per centimeter of length. 1 abampere = 1 abcoulomb/s = r statampere (where c = speed of light in cm/s) = 10 ampere. aberration Imperfect image formation due to geometric imperfections in the optical elements of a system ablation 1 . The wasting of glacier ice by any process (calving, melting, evaporation, etc.). 2. The shedding of molten material from the outer sur- face of a meteorite or tektite during its flight through the atmosphere. absolute age The age of a natural substance, of a fossil or living organism, or of an artifact, obtained by means of an absolute dating method. See absolute dating method. absolute density Density in kg/m' or, more commonly, in g/cm\ both at STP. Cf. density, relative density abso
Motion class 9 physics MCQ & SAQ
Motion class 9 physics ncert solution:
Q1: An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.
Answer: Yes an object can have zero displacement even though it has moved through a distance. It happens when the object moves back to its original position i.e. the final position coincides with the starting position.
Example: Suppose an object travels from O to C and then comes back to original position O.
Total distance traveled = actual path covered = OC CO = 25 25 = 50m
Total displacement = shortest distance between final position and initial position = 0m
Q2: What do you mean by a body in rest?
Answer: A body is said to be at rest, if it does not change its position with respect to a fixed point in its surroundings.
Q3: Are motion and rest absolute or relative? Explain with an example.
Answer: No these terms rest and motion are relative. For example, a person inside a car, carrying a ball in his hand will see the ball is at rest. While for another person, outside the car will see the ball is also moving.
Q4: What is meant by scalars and vectors?
Answer: Scalar Quantities: Quantities that require magnitudes only to specify them are called scalar quantities or scalars. Mass, length, time, temperature, angle, area, speed, distance, volume and density are examples of scalar quantities.
Vector Quantities: Quantities that require both magnitudes and direction to specify them are called vector quantities or vectors. Displacement, velocity, force, momentum, weight etc. are the examples of vectors.
Q5: A farmer moves along the boundary of a square field of 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20seconds?
Answer: As shown in figure, let us assume, the farmer starts from A.
Given, length of each side = 10m
Distance covered in 1 lap = Perimeter of ABCD = 4 x 10 = 40m
Time taken by farmer to cover 1 lap = 40s
Speed of farmer = Distance ÷ Time Taken for one lap = 40/40s = 1m/s
Distance covered by farmer in 2min 20 secs = Speed x Time = 1 x 140s = 140m
Number of laps covered = 140 ÷ 40 = 3.5 laps.
⇒ After 140s, the farmer will be at position C (i.e. 3 and ½ laps).
Displacement = AC = (AB2 BC2)½ (Pythagoras theorem)= (100 100)½=10√2 = 10 x 1.414 = 14.14m .... (answer)
Note: Displacement is a vector quantity that measures the shortest distance (straight line) between the starting point and ending point, not taking the actual path traveled into account.
Q6: Which of the following is true for displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than the distance traveled by the object.
Answer:
(a) False. Displacement can be zero. (See Q1).
(b) False. Displacement is less than or equal to the distance traveled by the object.
Q7: A particle moves along the x axis from A to B. Which Of the following values of
the initial and final coordinates, which results in a negative displacement?
Answer:
(a) False. Displacement can be zero. (See Q1).
(b) False. Displacement is less than or equal to the distance traveled by the object.
Q7: A particle moves along the x axis from A to B. Which Of the following values of
the initial and final coordinates, which results in a negative displacement?
(a) A = 4m, B = 6m
(b) A = −4m, B = −2m
(c) A = −4m, B = −8m
(d) A = −4m, B = 2m
Answer: (c)
Q8: Distinguish between speed and velocity.
Answer: *Speed -It is distance traveled by an object per unit time.Velocity-It is the displacement covered by an object per unit of time.
*Speed = distance ÷ time ; Velocity = displacement ÷ time
*Speed is a scalar quantity i.e. it has magnitude only. VelocityI is vector quantity i.e. has both magnitude and
direction.
Q9: Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?
Answer: When a body is in rectilinear motion i.e. moves in straight line, the magnitude of average velocity of an object is equal to its average speed.
Q10: What does the odometer of an automobile measure?
Answer: Odometer is used to measure the distance covered by the automobile. It also tells the instant speed of the vehicle. It can be mechanical or electronic or electromechanical.
Q11: What does the path of an object look like when it is in uniform motion?
Answer: When an object is in uniform motion, it means its speed is constant. Or it travels equal distance in equal intervals of time. The path may be a straight line or curved or zigzag. Its direction may also vary but the magnitude is fixed.
Q12: What is the average velocity over the “round trip” of an object that is thrown straight up from the ground and falls straight back down to the ground?
Answer: Total displacement in this case ("round trip") = 0m
Let us assume time taken = T secs.
Average velocity (v) = Total Displacement ÷ Time Taken = 0 ÷ T = 0 m/sec
Note: In the above question, there are two important words "round trip" and "average velocity".
While solving numericals, focus on such words. These two words help in understanding we need to compute displacement not distance. If average speed is being asked, we need to compute distance traveled.
Q13: During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station?
The signal travels at the speed of light, that is, 3 × 108 m s–1.
Answer: Given Time Taken (t) = 5 min = 5 x 60s = 300 s
Speed of signal (v) = 3 × 108 m s–1
Distance of spaceship = v x t = 3 × 108 m s–1 x 300 = 9 x 1010 m= 9 x 107 km
Note: When to take Average speed is equal to average mean of speeds and When to take Average Speed is equal to harmonic mean of speed?
Q14: Consider the following two scenarios and tell in which case average speed is
harmonic mean or arithmetic mean?
Case 1: A fellow travels from city A to city B. For the first hour, he drove at the constant speed of 20 km/hr. Then he (instantaneously) increased his speed and, for the next hour, kept it at 30 km per hour. Find the average speed of the motion.
Case 2: A fellow travels from city A to city B. The first half of the way, he drove at the constant speed of 20 km per hour. Then he (instantaneously) increased his speed and traveled the remaining distance at 30 km per hour. Find the average speed of the motion.
Answer:
Case 1: Arithmetic mean i.e. avg speed = (20 30)/2 = 25 km/hr
Case 2: Harmonic mean i.e. avg speed = 2/(1/20 1/30) = 24 km/hr
Q15: A cyclist cycles for a second at a speed of 3 m/s and then for the same time at a speed of 5 m/s along a straight road due north. What is the average speed of the cyclist?
Answer: You may compute arithmetic to compute average speed.
Alternately,
Total Time taken = 2t seconds
Total Distance covered = 3t 5t = 8t m
Avg. Speed = Total Distance / Total Time = 8t/2t = 4m/s ... (answer)
Q16: When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Answer:(i) A body is said to be in uniform acceleration if it travels in a straight line and its velocity increases or decreases by equal amounts in equal intervals of time.
(ii) A body is said to be in nonuniform acceleration if the rate of change of its velocity is not constant in equal intervals of time.
Q18: A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
Answer:Given,
Initial speed of bus (u) = 80 km/h = 80 x 1000/(60 x 60) = 800/36 m/s
Final speed of bus (v) = 60 km/h = 60 x 1000/3600 = 600/36 m/s
Time taken (t) = 5s
Since v = u at
a = (v u)/
t = (800600)/(
36 x 5) = 1.11 m s–2 ...(answer)
Q19: A train starting from a railway station and moving with uniform acceleration attains a speed of 40 km/h in 10 minutes. Find its acceleration.
Answer: Given,
Initial speed of train (u) = 0 km/hr
Final Speed of train (v) = 40 km/hr
Time taken = 10 min = 10/60 = 1/6 hr
Since v = u at
a = (vu)/
t = (400)/(
1/6) = 40 x 6 = 240 km hr–2 ...(answer)
Q20: A bus starting from rest moves with a uniform acceleration of 0.1 ms–2 for 2 minutes. Find (a) the speed acquired, (b) the distance traveled.
Answer: Given,
Initial speed (u) = 0 m/s
Acceleration of bus (a) = 0.1 ms–2
Time taken (t) = 2 min = 2 x 60 = 120 s
Final velocity = ?
Distance Covered (S) = ?
v = u at = 0 0.1 x 120 = 12 m/s ... (answer)
S = ut ½at2 = 0 (0.1 x 1202 )/2 = 0.1 x 14400 /2 = 720m ...(answer)
Q21: A train is traveling at a speed of 90 kmh–1. Brakes are applied so as to produce a uniform acceleration of – 0.5 ms–2. Find how far the train will go before it is brought to rest.
Answer: Given,
Initial Velocity of train (u) = 90 kmh–1 = 90 x 1000/ 3600 = 25 ms–1
Final velocity (v) = 0 ms–1
acceleration (a) = 0.5 ms–2
v2-u2= 2aS
⇒ S = (v2-u2) / 2a = 625/1= 625m ... (answer)
Q22: A trolley, while going down an inclined plane, has an acceleration of 2 cm s–2. What will be its velocity 3 s after the start?
Answer: Given,
Initial velocity (u) = 0 cm s–1.
acceleration (a) = 2 cm s–2.
time taken (t) = 3 s
v = u at
⇒ v = 0 2 x 3 = 6 cm s–1... (answer)
Q23: A racing car has a uniform acceleration of 4 m s–2. What distance will it cover in 10 s after start?
Answer: Given,
Initial velocity of car (u) = 0 m s–1.
acceleration (a) = 4 m s–2.
time taken (t) = 10 s
Distance covered (S) = ?
S = ut ½at2= 0 4x100/2 = 400 / 2 = 200 m ... (answer)
Q25: A train is running at a speed of 72 km/h. It crosses a bridge of half a kilometer in 1 minute. Calculate the length of the train.
Answer: Given,
Speed of the train (v) = 72kmph = 72 * 1000/3600 = 20 m s–1.
Length of bridge = 1/2 km = 500 m ...(I)
Time taken by train to cross bridge = 1min = 60s
Distance traveled by the train in the 60s = 20 x 60 = 1200m ....(II)
Length of train = (II)
(I) = 1200-500 = 700m ...(answer)
Q26: What is the nature of the distance time graphs for uniform and nonuniform motion of an object?
Answer: (a) When an object moves with uniform (constant) speed, it covers equal distances in equal intervals of time. It will make a straight line on the distance time graph making an angle with the time (x axis) axis.
(b) For an object moving in a non uniform motion will cover unequal distances in equal intervals of time. It will be a curve on a distance time graph.
Q27: What does the slope of distance time
graph indicate?
Answer: Slope indicates the speed of the object.
Q28: A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
Answer: (a) magnitude only
Q28: Which of the following situations is impossible to have?
Scene I: Object moving to east with velocity (v) and acceleration is acting towards
west.
Scene II: Object is moving with variable velocity but fixed acceleration.
Scene III: Object is moving with uniform velocity but non uniform
acceleration.
Scene IV: Object is moving with uniform speed but variable acceleration.
Answer: (c) Scene III is impossible to occur.
(Note: Scene I is possible. e.g. a car is moving towards east and brakes are applied. Retardation occurs in the opposite direction.)
Scene II is another common scenario. e.g. a free falling body, the velocity of the falling object increases every second but acceleration due to gravity is fixed.
Scene IV is possible: An object is in uniform circular motion i.e. it has fixed speed but direction of the object is changing every moment (direction of centripetal acceleration changes.)
Q29: A driver of a car traveling at 52 km/h applies the brakes and accelerates
uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3
km/h in another car applies his brakes slowly and stops in 10 s. On the same graph
paper, plot the speed versus time graphs for the two cars. Which of the two cars
traveled farther after the brakes were applied?
Answer:
Car A: Initial speed (uA) = 52km/h = 52 x 1000/3600 = 14.4 m/s
Final Speed (vA) = 0 m/s
Time taken (tA) = 5s
Car B: Initial speed (uB) = 3km/h = 3 x 1000/3600 = 0.83 m/s
Final Speed (vB) = 0 m/s
Time taken (tB) = 10s
Distance covered by car A = Area of △ AOB = ½ x AO x OB = ½ x 14.4 x 5 = 36m
Distance covered by car B = Area of △XOY = ½ x OX x OY = ½ x 0.83 x 10 = 4.15 m
⇒ Car A covers more distance as compared to car B.
Q30(NCERT): Fig (below) shows the distance time graph of three objects A,B and C.
Study the graph and answer the following questions:
(a) Which of the three is traveling the fastest?
(b) Are all three ever at the same point on the road?
(c) How far has C traveled when B passes A?
(d) How far has B traveled by the time it passes C?
Answer:
(a) Object B is traveling the fastest. We can determine it in two ways. Slope of the distance time line represents the speed of the object. In this case, object B has the highest slope.
(Note: slope is also represented by the angle subtended by the distance time line with x axis. Steeper the angle, higher the speed.)
(b) Not all objects never meet at the same point.
(c) When B and A meet at point m, Object C is at n, which is approximately 8km on the distance axis.
(d) B meets C at point k. The position on the distance axis is 9 units away from origin O.
One unit on the distance axis = 4/7 (7 units = 4km). ∴ Object B is = 9 x 4/7 = 5.14 km.
Q31: The speed time graph for a car is shown in the figure below. (a) Find how far the car travels in the first 4 seconds. Shade the area on the graph that represents the distance traveled by the car during the period. (b) Which part of the graph represents uniform motion of the car?
Answer:
(a) The green shaded area in the graph above shows the distance traveled by the car in the first 4 seconds. Taking approximation, the shaded area is a triangle. Distance covered in first 4s = Area of green shaded △ = 4 x 6 /2 = 12m.
(b) The line segment AB represents uniform motion of the car i.e. car after 6s attains
uniform motion.
Q32: The equation v = u at gives information as
(a) velocity is a function of time.
(b) velocity is a function of position.
(c) Position is a function of time.
(d) Position is a function of velocity and time.
Answer: (a) velocity is a function of time
Q33: The equation S = ut ½at2 gives information as
(a) velocity is a function of time.
(b) velocity is a function of position.
(c) Position is a function of time.
(d) Position is a function of velocity and time.
Answer: (d) Position is a function of velocity and time.
Q34: What will be the initial velocity of an object under free fall?
Answer: Zero m/s
Q35: Mathematically prove that the distance (S) traveled by an object is the average mean of initial velocity(u) and final velocity(v) having constant acceleration(a) in the direction of motion in a straight line.
Answer: To prove S = ½(u v)t
We know that v = u at
and 2aS = v2-u2
⇒ 2aS = (v-u)(v u) [∵ Algebraic identity (a2-b2)= (a b)(a-b)]
⇒ 2aS = (v u)at [using v-u= at]
⇒ 2S = (v u)t or S = ½(u v)t
⇒ (u v)/2 is the average velocity.
Q36: Orbit of an artificial satellite at a distance of 42260 km from earth is circular. It completes one revolution around the earth in 24 hours. Calculate its linear speed.
Answer: Linear speed in uniform circular motion = Circumference ÷ time = 2Ï€r ÷ t
Given, 42,260 km, t = 24 h
⇒ v = 2 ✕ 3.14 ✕ 42260 ÷ 24 = 11058.03 km/hr
Motion class 9 physics MCQ:
Question: From the given v-t graph (figure) it can be inferred that the object is moving with
a) uniform velocity
b) non uniform velocity
c) At rest
d) moving with uniform acceleration
Answer: uniform velocity
Question: What does the slope of distance - time graph give?
a) acceleration
b) both[a] and [c] depending upon the time of graph
c) Speed
d) uniform speed
Answer: acceleration
Question: In the total journey the body has traveled up to a distance of
a) 270m
b) 800m
c) 1000m
d) 900m
Answer: 270m
Question: The velocity of the body at the point B is
a) 36m/s
b) 20m/s
c) 40m/s
d) 50m/s
Answer: 36m/s
Question: At the point A the body is at a distance of
a) 180m
b) 200m
c) 300m
d) 50m
Answer: 180m
Question: Distance covered by the body during the interval from 10sec to 20 sec is
a) 270m
b) 200m
c) 360m
d) 400m
Answer: 270m
Question: From the figure the body is moving with
a) Constant Acceleration
b) Zero velocity
c) Variable Acceleration
d) Zero Acceleration
Answer: Constant Acceleration
Question: Distance covered by a body from velocity-time graph is
a) Area under the graph
b) Equal to the slope of the graph
c) Is denoted by a line parallel to the time axis at any point on the distance axis
d) Is denoted by a line parallel to the distance axis at any point on the time axis
Answer: Area under the graph
Question: The acceleration of a body from a velocity - time graph is
a) Equal to the slope of the graph
b) Area under the graph
c) Is denoted by a line parallel to the time axis at any point on the distance axis
d) Is denoted by a line parallel to the distance axis at any point on the time axis
Answer: Equal to the slope of the graph
Question: An example of a body moving with constant speed but still accelerating is
a) A body moving with constant speed in a circular path
b) A body moving with constant speed on a straight road
c) A body moving in a helical path with constant speed
d) A body moving with constant speed on a straight railway track
Answer: A body moving with constant speed in a circular path
Question: SI Unit of measurement of acceleration is
a) m/s2
b) m/s
c) M
d) m/hr
Answer: m/s2
Question: Formula to find the average velocity of a body is given by
a) Vav=(u + v)/2
b) Sn ={u + a/2(2n-1)}
c) S= ut + 1/2 a t2
d) V= u + at
Answer: Vav=(u + v)/2
Question: An object travels 20m in 5 sec and then another 40m in 5 se What is the average speed of the object?
a) 6m/s
b) 0 m/s
c) 12m/s
d) 2m/s
Answer: 6m/s
Question: A farmer moves along the boundary of a square field of side 10 m in 40 sec. The magnitude of displacement of the farmer at the end of 2 minutes 20 seconds from his initial position is
a) 10 `sqrt(2m)`
b) 30m
c) 10m
d) 40m
Answer: 10 `sqrt(2m)`
Question: A man travels a distance of 20 km from his home to office, and 10 km towards his house back. Then the displacement covered by the man in the whole trip is
a) 10 Km
b) 30 Km
c) zero Km
d) 50 Km
Answer: 10 Km
Question: Acceleration is a vector quantity, which indicates that its value
a) Can be positive, negative or zero
b) Is always positive
c) Is always negative
d) Is zero
Answer: Can be positive, negative or zero
Question: Rate of change of displacement is called
a) Velocity
b) deceleration
c) Speed
d) acceleration
Answer: Velocity
Question. 180° plane angle is equal to
(a) π/2 radian
(b) π radian
(c) 2Ï€ radian
(d) none of these
Answer: B
Question. Suppose a boy is enjoying a ride on a marry-go-round which is moving with a constant speed of 10 m/s. It implies that the boy is:
(a) At rest
(b) Moving with no acceleration
(c) In accelerated motion
(d) Moving with uniform velocity
Answer: C
Question. 1 km/ h = ________ m/s
(a) 3/50
(b) 18/5
(c) 50/3
(d) 5/18
Answer: D
Question. Which of the following statements is correct regarding velocity and speed of a moving body?
(a) Velocity of a moving body is always higher than its speed
(b) Speed of a moving body is always higher than its velocity
(c) Speed of a moving body is its velocity in a given direction
(d) Velocity of a moving body is its speed in a given direction
Answer: D
Question. If car A is at 40 km/h and car B is at 10 km/h in the opposite direction, what is the velocity of car A relative to car B?
(a) 40 km/h
(b) 50 km/h
(c) 10 km/h
(d) 30 km/h
Answer: B
Question. Which of the following is most likely not a case of uniform circular motion?
(a) Motion of the earth around the sun
(b) Motion of a toy train on a circular track
(c) Motion of a racing car on a circular track
(d) Motion of hours’ hand on the dial of a clock
Answer: C
Question. A man is moving at 36 kmph. The time of reaction is 0.9 seconds. On seeing an obstacle in the path, he applies brakes and decelerates at 5 m/s2, the total distance covered before he stops is:
(a) 19 m
(b) 17 m
(c) 16 m
(d) 18 m
Answer: A
Question. The numerical ratio of displacement to distance for a moving object is:
(a) Always less than 1
(b) Equal to 1 or less than 1
(c) Always more than 1
(d) Equal to 1 or more than one
Answer: B
Question. A car goes from town A to another town B with a speed of 40 km/h and returns back to town A with a speed of 60 km/h. The average speed of the car during the complete journey is -
(a) 48 km/h
(b) 50 km/h
(c) zero
(d) none of these.
Answer: A
Question.______________ _ describes how fast something is going, whereas, __________ describes how fast something is going in a certain direction.
(a) rate, velocity
(b) rate, speed
(c) speed, velocity
(d) speed, acceleration
Answer: C
Question. Which of the following is a correct measure of velocity?
(a) 30 s
(b) 30 m/s
(c) 30 South
(d) 30 m/s, South
Answer: D
Question. The speed at any instant of time is known as
(a) velocity
(b) given speed
(c) average speed
(d) instantaneous speed
Answer: D
Question. The slope of the distance-time graph is:
(a) Distance
(b) acceleration
(c) Speed
(d) Displacement
Answer: C
Question. In 12 minutes a car whose speed is 35 km/h travels a distance of
(a) 7 km
(b) 3.5 km
(c) 14 km
(d) 28 km
Answer: A
Question. A body moves in a uniform circular motion
(a) it is moving with constant velocity.
(b) its acceleration is zero
(c) the body has an acceleration
(d) none of these
Answer: C
Question. A body whose speed is constant
(a) must be accelerated
(b) might be accelerated
(c) has a constant velocity
(d) can not be accelerated.
Answer: B
Question. The S.I. unit of acceleration is:
(a) ms-2
(b) ms
(c) ms2
(d) m
Answer: C
Question. A particle experiences constant acceleration for 20 seconds after starting from rest. If it travels a distance s1 in the first 10 seconds and distance s2 in the next 10 seconds then,
(a) s2 = s1
(b) s2 = 2s1
(c) s2 = 3s1
(d) s2 = 4s1
Answer: C
Question. A boy throws a ball up and catches it when the ball falls back. In which part of the motion the ball is accelerating?
(a) During downward motion
(b) When the ball comes to rest
(c) During upward motion
(d) When the boy catches the ball
Answer: A
Question. Speed of a body in particular direction can be called
(a) acceleration
(b) displacement
(c) velocity
(d) distance
Answer: C
Question. A body performs an accelerated motion, with uniform speed. The motion of body is
(a) Linear
(b) Circular
(c) Parabolic
(d) Irregular
Answer: B
Question. Choose the correct option:
(a) distance is a scalar, velocity is a vector , acceleration is a vector.
(b) distance is a vector, velocity is a scalar, acceleration is a vector.
(c) distance is a vector, velocity is a vector, acceleration is a vector.
(d) distance is a scalar, velocity is a vector, acceleration is a scalar.
Answer: A
1. Which of the following statements is correct regarding velocity and speed of a moving body?
(a) Velocity of a moving body is always higher than its speed
(b) Speed of a moving body is always higher than its velocity
(c) Speed of a moving body is its velocity in a given direction
(d) Velocity of a moving body is its speed in a given direction
► (d) Velocity of a moving body is its speed in a given direction
2. The slope of the distance-time graph is:
(a) Distance
(b) acceleration
(c) Speed
(d) Displacement
► (c) Speed
3. For a body performing motion with uniform speed, the distance-time graph is:
(a) Straight line parallel to y-axis
(b) Straight line inclined to the time axis
(c) Straight line parallel to x-axis
(d) Curved line
► (b) Straight line inclined to the time axis
4. Which of the following is a correct measure of velocity?
(a) 30 s
(b) 30 m/s
(c) 30 South
(d) 30 m/s, South
► (d) 30 m/s, South
5. An object travels 20 m in 5 sec and then another 40 m in 5 sec. What is the average speed of the object?
(a) 6 m/s
(b) 2 m/s
(c) 12 m/s
(d) 0 m/s
► (a) 6 m/s
6. A body moves in a uniform circular motion
(a) it is moving with constant velocity.
(b) its acceleration is zero
(c) the body has an acceleration
(d) none of these
► (c) the body has an acceleration
7. The S.I. unit of acceleration is:
(a) ms-2
(b) ms
(c) ms2
(d) m
► (c) ms2
8. What is the average velocity of a car that moved 60 km in 3 hours?
(a) 60 km/h
(b) 20 km/h
(c) 30 km/h
(d) 10 km/h
► (b) 20 km/h
9. Which of the following situations are not possible?
(a) A body moving with constant acceleration but with zero velocity.
(b) A body moving horizontally with an acceleration in vertical direction
(c) A body moving with a constant velocity in an accelerated motion
(d) All of these
► (c) A body moving with a constant velocity in an accelerated motion
10. A boy throws a ball up and catches it when the ball falls back. In which part of the motion the ball is accelerating?
(a) During downward motion
(b) When the ball comes to rest
(c) During upward motion
(d) When the boy catches the ball
► (a) During downward motion
11. Choose the correct option:
(a) distance is a scalar, velocity is a vector , acceleration is a vector.
(b) distance is a vector, velocity is a scalar, acceleration is a vector.
(c) distance is a vector, velocity is a vector, acceleration is a vector.
(d) distance is a scalar, velocity is a vector, acceleration is a scalar.
► (a) distance is a scalar, velocity is a vector , acceleration is a vector.
12. Name the instrument used to measure instantaneous speed of a vehicle
(a) multimeter
(b) ammeter
(c) speedometer
(d) accelerator
► (c) speedometer
13. 180° plane angle is equal to
(a) π/2 radian
(b) π radian
(c) 2Ï€ radian
(d) none of these
► (b) Ï€ radian
14. The area under the speed-time graph gives the ________.
(a) velocity
(b) distance
(c) acceleration
(d) time
► (b) distance
15. 1 km/ h = ________ m/s
(a) 3/50
(b) 18/5
(c) 50/3
(d) 5/18
► (d) 5/18
16. The ratio of the heights from which two bodies are dropped is 3:5 respectively. The ratio of their final velocities is:
(a) 9: 25
(b) √ 3: √ 5
(c) 5 : 3
(d) √5 : √3
► (b) √ 3: √ 5
17. The speed at any instant of time is known as
(a) velocity
(b) given speed
(c) average speed
(d) instantaneous speed
► (d) instantaneous speed
18. A racing car has a uniform acceleration of 6 m/s2. In 10s it will cover:
(a) 300m
(b) 100m
(c) 200m
(d) 350m
► (a) 300m
19. A body starts to slide over a horizontal surface with an initial velocity of 0.2 m/s. Due to friction, its velocity decreases at the rate of 0.02 m/s2. How much time will it take for the body to stop?
(a) 10s
(b) 15s
(c) 1s
(d) 5s
► (a) 10s
20. The equations of motion can be derived by using:
(a) Distance – time graph
(b) Velocity – time graph for non-uniform acceleration
(c) Displacement time graph
(d) Velocity – time graph for uniform acceleration
► (d) Velocity – time graph for uniform acceleration
21. A man is moving at 36 kmph. The time of reaction is 0.9 seconds. On seeing an obstacle in the path, he applies brakes and decelerates at 5 m/s2, the total distance covered before he stops is:
(a) 19 m
(b) 17 m
(c) 16 m
(d) 18 m
► (a) 19 m
22. Speed of a body in particular direction can be called
(a) acceleration
(b) displacement
(c) velocity
(d) distance
► (c) velocity
23. The ratio of C.G.S. to M.K.S. unit of acceleration is:
(a) 1:10
(b) 1:1
(c) 1:100
(d) 10:1
► (c) 1:100
29. Distance covered by a body from velocity-time graph is
(a) Equal to the slope of the graph.
(b) Area under the graph .
(c) Is denoted by a line parallel to the time axis at any point on the distance axis.
(d) Is denoted by a line parallel to the distance axis at any point on the time axis.
► (b) Area under the graph .
30. A body performs an accelerated motion, with uniform speed. The motion of body is
(a) Linear
(b) Circular
(c) Parabolic
(d) Irregular
► (b) Circular
31. The slope of distance – time graph gives instantaneous.
(a) acceleration
(b) speed
(c) velocity
(d) Distance covered
► (b) speed
32. ______________ _ describes how fast something is going, whereas, __________ describes how fast something is going in a certain direction.
(a) rate, velocity
(b) rate, speed
(c) speed, velocity
(d) speed, acceleration
► (c) speed, velocity
33. If a moving body comes to rest, then its acceleration is-
(a) positive
(b) both of these depending upon the initial velocity
(c) negative
(d) zero
► (c) negative
34. If car A is at 40 km/h and car B is at 10 km/h in the opposite direction, what is the velocity of car A relative to car B?
(a) 40 km/h
(b) 50 km/h
(c) 10 km/h
(d) 30 km/h
► (b) 50 km/h
35. Speed of 90 km/h when expressed in m/s is
(a) 2.5
(b) 90000
(c) 250
(d) 25
► (d) 25
1. Which of the following statements is correct regarding velocity and speed of a moving body?
(a) Velocity of a moving body is always higher than its speed
(b) Speed of a moving body is always higher than its velocity
(c) Speed of a moving body is its velocity in a given direction
(d) Velocity of a moving body is its speed in a given direction
► (d) Velocity of a moving body is its speed in a given direction
2. The slope of the distance-time graph is:
(a) Distance
(b) acceleration
(c) Speed
(d) Displacement
► (c) Speed
3. For a body performing motion with uniform speed, the distance-time graph is:
(a) Straight line parallel to y-axis
(b) Straight line inclined to the time axis
(c) Straight line parallel to x-axis
(d) Curved line
► (b) Straight line inclined to the time axis
4. Which of the following is a correct measure of velocity?
(a) 30 s
(b) 30 m/s
(c) 30 South
(d) 30 m/s, South
► (d) 30 m/s, South
5. An object travels 20 m in 5 sec and then another 40 m in 5 sec. What is the average speed of the object?
(a) 6 m/s
(b) 2 m/s
(c) 12 m/s
(d) 0 m/s
► (a) 6 m/s
6. A body moves in a uniform circular motion
(a) it is moving with constant velocity.
(b) its acceleration is zero
(c) the body has an acceleration
(d) none of these
► (c) the body has an acceleration
7. The S.I. unit of acceleration is:
(a) ms-2
(b) ms
(c) ms2
(d) m
► (c) ms2
8. What is the average velocity of a car that moved 60 km in 3 hours?
(a) 60 km/h
(b) 20 km/h
(c) 30 km/h
(d) 10 km/h
► (b) 20 km/h
9. Which of the following situations are not possible?
(a) A body moving with constant acceleration but with zero velocity.
(b) A body moving horizontally with an acceleration in vertical direction
(c) A body moving with a constant velocity in an accelerated motion
(d) All of these
► (c) A body moving with a constant velocity in an accelerated motion
10. A boy throws a ball up and catches it when the ball falls back. In which part of the motion the ball is accelerating?
(a) During downward motion
(b) When the ball comes to rest
(c) During upward motion
(d) When the boy catches the ball
► (a) During downward motion
11. Choose the correct option:
(a) distance is a scalar, velocity is a vector , acceleration is a vector.
(b) distance is a vector, velocity is a scalar, acceleration is a vector.
(c) distance is a vector, velocity is a vector, acceleration is a vector.
(d) distance is a scalar, velocity is a vector, acceleration is a scalar.
► (a) distance is a scalar, velocity is a vector , acceleration is a vector.
12. Name the instrument used to measure instantaneous speed of a vehicle
(a) multimeter
(b) ammeter
(c) speedometer
(d) accelerator
► (c) speedometer
13. 180° plane angle is equal to
(a) π/2 radian
(b) π radian
(c) 2Ï€ radian
(d) none of these
► (b) Ï€ radian
14. The area under the speed-time graph gives the ________.
(a) velocity
(b) distance
(c) acceleration
(d) time
► (b) distance
15. 1 km/ h = ________ m/s
(a) 3/50
(b) 18/5
(c) 50/3
(d) 5/18
► (d) 5/18
16. The ratio of the heights from which two bodies are dropped is 3:5 respectively. The ratio of their final velocities is:
(a) 9: 25
(b) √ 3: √ 5
(c) 5 : 3
(d) √5 : √3
► (b) √ 3: √ 5
17. The speed at any instant of time is known as
(a) velocity
(b) given speed
(c) average speed
(d) instantaneous speed
► (d) instantaneous speed
18. A racing car has a uniform acceleration of 6 m/s2. In 10s it will cover:
(a) 300m
(b) 100m
(c) 200m
(d) 350m
► (a) 300m
19. A body starts to slide over a horizontal surface with an initial velocity of 0.2 m/s. Due to friction, its velocity decreases at the rate of 0.02 m/s2. How much time will it take for the body to stop?
(a) 10s
(b) 15s
(c) 1s
(d) 5s
► (a) 10s
20. The equations of motion can be derived by using:
(a) Distance – time graph
(b) Velocity – time graph for non-uniform acceleration
(c) Displacement time graph
(d) Velocity – time graph for uniform acceleration
► (d) Velocity – time graph for uniform acceleration
21. A man is moving at 36 kmph. The time of reaction is 0.9 seconds. On seeing an obstacle in the path, he applies brakes and decelerates at 5 m/s2, the total distance covered before he stops is:
(a) 19 m
(b) 17 m
(c) 16 m
(d) 18 m
► (a) 19 m
22. Speed of a body in particular direction can be called
(a) acceleration
(b) displacement
(c) velocity
(d) distance
► (c) velocity
23. The ratio of C.G.S. to M.K.S. unit of acceleration is:
(a) 1:10
(b) 1:1
(c) 1:100
(d) 10:1
► (c) 1:100
29. Distance covered by a body from velocity-time graph is
(a) Equal to the slope of the graph.
(b) Area under the graph .
(c) Is denoted by a line parallel to the time axis at any point on the distance axis.
(d) Is denoted by a line parallel to the distance axis at any point on the time axis.
► (b) Area under the graph .
30. A body performs an accelerated motion, with uniform speed. The motion of body is
(a) Linear
(b) Circular
(c) Parabolic
(d) Irregular
► (b) Circular
31. The slope of distance – time graph gives instantaneous.
(a) acceleration
(b) speed
(c) velocity
(d) Distance covered
► (b) speed
32. ______________ _ describes how fast something is going, whereas, __________ describes how fast something is going in a certain direction.
(a) rate, velocity
(b) rate, speed
(c) speed, velocity
(d) speed, acceleration
► (c) speed, velocity
33. If a moving body comes to rest, then its acceleration is-
(a) positive
(b) both of these depending upon the initial velocity
(c) negative
(d) zero
► (c) negative
34. If car A is at 40 km/h and car B is at 10 km/h in the opposite direction, what is the velocity of car A relative to car B?
(a) 40 km/h
(b) 50 km/h
(c) 10 km/h
(d) 30 km/h
► (b) 50 km/h
35. Speed of 90 km/h when expressed in m/s is
(a) 2.5
(b) 90000
(c) 250
(d) 25
► (d) 25
36. A body is moving with a velocity of 10m/s. If the motion is uniform, what will be the velocity after 10 second?
(a) 15m/s.
(b) 5m/s
(c) 10m/s
(d) 20m/s
► (c) 10m/s
37. A body is said to be in rest when
(a) its position doesn’t change with time with respect to the observer.
(b) body moves in uniform motion w.r.t observer
(c) its position changes with time w.r.t observer.
(d) none of these
► (a) its position doesn’t change with time with respect to the observer.
38. If you whirl a stone on the end of the string and the string suddenly breaks, the stone will:
(a) Fly off along the tangent to its circular path.
(b) Fly directly towards you.
(c) Spiral away from your hand.
(d) Spiral in towards your hand.
► (a) Fly off along the tangent to its circular path.
Motion class 9 physics SAQ:
Under what condition is distance and the magnitude of the displacement equal ?
(CBSE 2010, 2013, 2014, 2015)
Distance and magnitude of the displacement are equal if an object moves along a straight line in one direction.
What do you mean by uniform motion ? (CBSE 2010, 2012)
Answer:
The motion of an object is uniform motion if it travels equal distances in equal intervals of time along a straight line.
What is non-uniform motion ? (CBSE 2012)
Answer:
The motion of an object is non-uniform if it travels unequal distances in equal intervals of time.
Give one example of non-uniform motion. (CBSE 2012)
Answer:
A bus moving on a hilly road or on a zig-zag road.
Define average speed. (CBSE 2012)
Answer:
Average speed is the ratio of the total distance traveled by an object to the total time taken by it.
What do you understand by a uniform velocity ?
Or
When is a body said to have uniform velocity ? (CBSE 2011, 2012, 2013)
Answer:
Velocity of an object is uniform if it has equal displacements in equal intervals of time.
What do you understand about a non-uniform velocity ?
Or
When is a body said to have non-uniform velocity ? (CBSE 2011)
Answer:
Velocity of an object is non-uniform if it has unequal displacements in equal intervals of time.
An object starts with initial velocity u and attains final velocity V. The velocity is changing at a uniform rate.
What is the formula for calculating average speed in this situation ? (CBSE 2011)
Answer:
What is the numerical ratio of average velocity to average speed of an object when it is moving along a straight path ? (CBSE 2014)
Answer:
In this case, both are equal, so the ratio is 1.
Based on Acceleration
What do you mean by positive acceleration ? (CBSE 2013, 2015)
Answer:
When the change in velocity of a body takes place in the direction of motion of the body, then the acceleration is positive.
What do you mean by negative acceleration ? (CBSE 2015)
Answer:
When the change in velocity of a body takes place in a direction opposite to the direction of motion of the body, then the acceleration is negative.
Give one example of retardation or negative acceleration. (CBSE 2013)
Answer:
When the velocity of a train decreases before entering the platform.
When do you say that a body is in uniform acceleration ? (CBSE 2010, 2013)
Or
Define uniform acceleration. (CBSE 2010, 2013, 2014, 2015)
Answer:
When the velocity of a body changes by an equal amount in equal intervals of time, then the body is in uniform . acceleration.
When do you say that a body has non-uniform acceleration ? (CBSE 2013)
Answer:
When the velocity of a body changes by unequal amount in equal intervals of time, then the body is in non¬uniform acceleration
What would you say about the motion of a body if its distance-time graph is a straight line having a constant angle with a time axis ? (CBSE 2010)
Answer:
If the distance-time graph is a straight line having a constant angle with the time axis, then the distance traveled by the body increases in equal amounts in equal intervals of time. It means, the motion of the body is a uniform motion.
If the displacement-time graph for a particle is parallel to the time axis, how much is the velocity of the particle.
(CBSE 2013)
Answer:
Velocity is zero as there is no change in displacement with time.
What does the slope of a velocity-time graph represent ?(CBSE 2010, Term I)
It represents the acceleration of the body.
Figure shows the displacement-time graph of four children A, B, C and D. Which child has the highest velocity ? (CBSE 2010, 2012, 2013)
Answer:
Velocity = Slope of displacement – time graph.
Since slope of displacement-time graph for child B is greater than all other children. Hence, child B has the highest velocity.
What can you say about the motion of a body if its velocity-time graph is a straight line parallel to the time axis ?
(CBSE 2012)
Answer:
When the velocity-time graph of the motion of a body is a straight line parallel to the time axis, then the velocity of the body does not change with time. So the body is said to move with constant velocity.
Name the physical quantity measured by the area occupied below the velocity-time graph for uniform motion.
(CBSE 2012, 2014)
Answer:
Magnitude of displacement of the body = area under v-t graph.
Plot velocity-time graph of a body moving with constant or uniform velocity. (CBSE 2012, 2014)
Answer:
Velocity-time graph of a body is shown in figure A.
What conclusion can be drawn about the type of motion ? (CBSE 2010, 2011, 2012)
Answer:
Motion of the body is uniform motion.
Define circular motion. (CBSE 2011, 2012)
Answer:
The motion of a body moving around a fixed point in a circular path.
State the meaning of uniform circular motion.
(CBSE 2010, 2012, 2013, 2014, 2015)
Answer:
The circular motion of a body having constant speed is called uniform circular motion.
Give an example of a uniform circular motion. (CBSE 2014)
Answer:
A cyclist traveling with constant speed on a circular path.
Is uniform circular motion accelerated motion ?
(CBSE 2012, 2013)
Answer:
Uniform circular motion of a body is accelerated because its direction of motion changes continuously although its speed is constant.
Can a body exist in a state of absolute rest or of absolute motion ? Explain with examples. (CBSE 2015)
Answer:
A state of rest or state of motion is not absolute but it is a relative term. A body at rest in one frame of reference
may be in motion in another frame of reference. For example, a passenger sitting in a moving bus is at rest with respect to the bus or other co-passengers. However, the same passenger is in motion with respect to a person standing on a road side. Thus, rest and motion are relative terms.
Distinguish between distance and displacement. (CBSE 2010, 2012, 2013)
Answer:
Mention two differences between speed and velocity. (CBSE 2013, 2015)
Answer:
Give one example each to differentiate between uniform acceleration and non-uniform acceleration.
(CBSE 2010, 2012)
Answer:
Object has uniform acceleration if its velocity changes by an equal amount in equal intervals of time. For example, motion of an object falling freely from the top of a building.
On the other hand if velocity of an object changes by an unequal amount in equal intervals of time, then it has non-uniform acceleration. For example, the motion of a bus on a hilly track or on a circular track.
What is the difference between uniform motion in a straight line and uniform circular motion ?
(CBSE 2010, 2012, 2013)
Answer:
Motion class 9 physics long question:
Draw velocity-time graph for an uniformly accelerated object. Using a velocity-time graph, derive v = u + at.
Or
Derive the equation of motion V = u + at using a graphical method. (CBSE 2011, 2013, 2015)
Answer:
Derivation of First Equation of Motion From Velocity-Time Graph (Equation for Velocity-time Relation)
The velocity-time graph of a uniformly accelerated motion of the body having initial velocity (u) is shown in figure .
The velocity-time graph is a straight line AB.
Draw velocity-time graph for an uniformly accelerated object. Using the velocity-time graph, derive S = ut + ½ at² .
(CBSE 2010, 2011, 2013, 2015)
Or
From the velocity-time graph of a body, derive an equation for “position-time” relation (II equation of motion) for a body. (CBSE 2012)
Answer:
Draw velocity-time graph for an uniformly accelerated object. Using the velocity-time graph, derive v2 – u2 = 2aS.
(CBSE 2010, 2011, 2013)
Answer:
An object starts a linear motion with velocity ‘u’ and with acceleration ‘a’ It acquires a velocity ‘v’ in time ‘t’.
(i) Draw its velocity-time graph
(ii) Obtain 1st equation of motion, v = u + at for velocity time relation using this graph. (CBSE 2013)
Answer:
(i)
(ii)
Derivation of First Equation of Motion From Velocity-Time Graph (Equation for Velocity-time Relation)
The velocity-time graph of a uniformly accelerated motion of the body having initial velocity (u) is shown in figure 28.
The velocity-time graph is a straight line AB.
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