21. A man is sitting in a train which is moving with a velocity of 60 km/h. His speed with respect to the train is
(a) \(\frac{10}{3}\)m/s
(b) 60 m/s
(c) infinite
(d) zero
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22. Two parallel train tracks run from North to South. On one track train A is moving with a speed 30 m/s from North to South. An the other track a train B is moving with speed 50 m/s from South to North. The relative velocity of train A with respect to train B is
(a) 30 m/s
(b) 80 m/s
(c) 20 m/s
(d) 100 m/s
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23. In negative acceleration, the velocity of a body ………… .
(a) is zero
(b) increases
(c) decreases
(d) remains constant
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24. For a body moving with uniform acceleration its final velocity equals ……….. .
(a) average velocity − initial velocity
(b) 2 × average velocity − initial velocity
(c) 2 × average velocity + initial velocity
(d) average velocity + initial velocity
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25. Find the acceleration (in m/\(sec^{2}\)) of a body which accelerates from 10 m/s to 20 m/s in 4 seconds.
(a) 7.5
(b) 5
(c) 15
(d) 2.5
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26. Which of the following statements is false?
(a) A body can have zero velocity and still be accelerated.
(b) A body can have a constant velocity and still have a varying speed.
(c) A body can have a constant speed and still have varying velocity.
(d) the direction of the velocity of a body can change when its acceleration is constant.
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27. If an object moves with constant velocity, then which one of the following statement is not correct?
(a) Its motion is along a straight line.
(b) Its speed changes with time.
(c) Its acceleration is zero.
(d) Its displacement increases linearly with time.
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28. Which one of the following statements is not correct?
(a) If the velocity and acceleration have opposite sign, then the object is slowing down.
(b) If the velocity is zero at an instant, then the acceleration should also be zero at that instant.
(c) If the velocity is zero for a time interval, then the acceleration is zero at any instant within the time interval.
(d) If the position and velocity have opposite sign, then the object is moving towards the origin.
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29. If the distance S covered by a moving car in rectilinear motion with a speed v in time t is given by s=vt, then the car undergoes
(a) a uniform acceleration
(b) a non-uniform acceleration
(c) a uniform velocity
(d) a non-uniform velocity
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30. The acceleration of a particle at a particular instant of time is called
(a) average acceleration
(b) Instantaneous acceleration
(c) average velocity
(d) None of the above
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