NCERT Solutions for class 11 Physics | Chapter 3 - Motion in a Straight Line

Questions
1 At a metro station, a girl walks up a stationary escalator in time t1. If she remains stationary on the escalator, then the escalator take her up in time t2. The time taken by her to walk up on the moving escalator will be
A (t1 + t2)/2
B t1 t2 /(t2 – t1)
C t1t2 /(t2 + t1)
D t1 –t2

Answer:t1t2 /(t2 + t1)
2 For the one-dimensional motion, described by x = t–sint
A x (t) > 0 for all t > 0.
B v (t) > 0 for all t > 0.
C a (t) > 0 for all t > 0.
D v (t) lies between 0 and 2.

Answer:A, D

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3 A lift is coming from 8th floor and is just about to reach 4th floor. Taking ground floor as origin and positive direction upwards for all quantities, which one of the following is correct?
A x < 0, v < 0, a > 0
B x > 0, v < 0, a < 0
C x > 0, v < 0, a > 0
D x > 0, v > 0, a < 0

Answer:x < 0, v < 0, a > 0
4 A ball is bouncing elastically with a speed of 1m/s between walls of a railway compartment of size 10m in the direction perpendicular to walls. The train is moving at a constant speed of 10m/s parallel to the direction of motion of the ball. As seen from the ground,
A The direction of motion of the ball changes every 10 seconds.
B The speedd of the ball changes every 10 seconds.
C average speed of the ball over any 20 seconds interval is fixedy
D the acceleration of ball is the same as from the train.

Answer:B, C, D
5 A spring with one end attached to a mass m and other end to a rigid support is stretched and released.
A Magnitude of acceleration, when just released is maximum.
B Magnitude of acceleration, when at equilibrium position is maximum.
C Speed is maximum when mass is at equilibrium position.
D Magnitude of displacement is always maximum, whenever speed is maximum.

Answer:A, C
6 For the one-dimensional motion, described by x=t-sin t
A X(t)> 0 for all t>0
B V(t)>0 for all t>0
C A(t)>0for all t>0
D V(t) lies between 0 and 2

Answer:A, D
7 A graph of x versus t shown in x figure. Choose correct alternatives from below.

Motion In a Straight Line

A The particle was released from rest at t=0
B At B, the acceleration a>0
C At C, the velocity and acceleration vanishes.
D The speed at D exceeds that at E.

Answer:A, C, D
8 The variation of quantity A with quantity B, plotted in the figure. Describe the motion of a particle in a straight line.

Motion in a Straight line

A Quantity B may represent time.
B Quantity A is velocity if the motion is uniform.
C Quantity A is displacement if the motion is uniform.
D Quantity A is velocity if the motion is uniformly accelerated.

Answer:A, C, D
9 In one-dimensional motion, instantaneous V speed satisfies 0≤< v 0.
A The displacement in time T must always take non-negative values.
B The displacement x in time T satisfies -v0T< x < v 0T.
C The acceleration is always a non-negative number.
D The motion has no turning points.

Answer:The displacement x in time T satisfies -v0T0T.
10 A vehicle travels half the distance L with speed v1 and the other half with speed v2, then its average speed is
A Motion in a Straight Line
B Motion in a Straight Line
C Motion in a Straight Line
D Motion in a Straight Line

Answer:Motion in a Straight Line
11 The displacement of a particle is given by x= (t-2)2 where x is in meters and t in seconds. The distance covered by the particle in first 4 second is:
A 4m
B 8m
C 12m
D 16m

Answer:8m
12 Among the four graphs (Below the Fig.), there is only one graph for which average velocity over the time intervel (0, T ) can vanish for a suitably chosen T. Which one is it?

Motion in a Straight Line

A (a)
B (b)
C (c)
D (d)

Answer:(b)
13 The displacement of a particle is given by x = (t – 2)2 where x is in metres and t in seconds. The distance covered by the particle in first 4 seconds is
A 4 m
B 8 m
C 12 m
D 16 m

Answer:8 m
14 A body starts from rest . If it travels with an acceleration of 2 m/s2 , its displacement at the endof 3 seconds is
A 9 m
B 12 m
C 16 m
D 10 m

Answer:9 m
15 The displacement in metres of a body varies with time t in seconda as y = t2 - t - 2 . The displacement is zero for a positive of t equal to
A 1s
B 2s
C 3s
D 4s

Answer:2s
16 A boy starts from a point A, travels to a point B at a distance of 3 km from A and returns to A . If he takes two hours to do so, his speed is
A 3 km/h
B zero
C 2 km/h
D 1.5 km/h

Answer:3 km/h
17 Which one of the following is the unit of velocity ?
A kilogram
B metre
C m/s
D second

Answer:m/s
18 A body travels on a straight line with an initial velocity of 2 m/s . If its uniform acceleration is 1 m/s2 , its velocity at the end of 5 seconds is
A 5 m/s
B 7 m/s
C 9 m/s
D 6 m/s

Answer:7 m/s
19 Which one of the following is the unit of acceleration ?
A m/s
B m/s2
C km/hr
D cm/s

Answer:m/s2
20 A body starts from rest and travels for five seconds to make a displacement of 25 m .if it has travelled the distance with uniform acceleration a then a is
A 3 m/s2
B 4 m/s2
C 2 m/s2
D 1 m/s2

Answer:2 m/s2

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