1. Can earth be regarded as a point object when describing its yearly journey around the sun?
a) Yes
b) No
Explanation: Earth can be regarded as a point object when describing its yearly journey around the sun because the size of the earth is much smaller than the distance from the sun.
2. Displacement can be greater than the distance travelled by an object.
a) True
b) False
Explanation: The displacement of an object can be either equal to or less than the distance travelled by the object. This is because displacement is the shortest distance between the initial and final positions of the object while distance travelled is the length of the actual path traversed by the object.
3. Under what condition is the average velocity equal to the instantaneous velocity?
a) Varying velocity
b) Varying speed
c) Constant velocity
d) Constant speed
Explanation: When a body moves with a constant velocity, its average velocity over any time interval is same as instantaneous velocity.
4. How is the speed related to the magnitude of velocity?
a) Greater
b) Lesser
c) Equal
d) Doesn’t vary
Explanation: Due to change in direction of motion, the length of the path traversed by a body is generally greater than the magnitude of its displacement. So the speed is greater than the magnitude of the velocity.
5. Two balls of different masses (one lighter and one heavier) are thrown vertically upward with same initial speed. Which one will rise to a greater height?
a) The lighter one
b) The heavier one
c) Neither
d) Both the balls
Explanation: Both the balls will rise to the same height. It is because, for a body moving with given initial velocity and acceleration, the distance covered by the body does not depend on the mass of the body.
6. When rain falls vertically downwards, the front screen of a moving car gets wet while the back screen remains dry.
a) True
b) False
Explanation: When the rain is falling vertically downwards, the front screen of a moving car gets wet while back screen remains dry. This is because the rain strikes the car in the direction of relative velocity of rain with respect to the car.
7. Two trains A and B of length 400m each are moving on two parallel tracks with a uniform speed of 72km/h in the same direction, with A ahead of B. The driver of B decides to overtake A and accelerates by 1m/s. If after 50s, the guard of B just brushes past the driver of A, what is the original distance between them?
a) 50m
b) 150m
c) 125m
d) 1250m
Explanation: Let x be the distance between then driver of train A and the guard of train B. Initially, both trains are moving in the same direction with the same speed of 72km/h. So relative velocity of B with respect to A = vB-vA = 0. Hence the train B needs to cover a distance with a= 1m/s, t = 50 s, u = 0
s = ut + 1/2at2 = 1250m.
8. A player throws a ball upwards with an initial speed of 29.4m/s. What is the direction of acceleration during the upwards motion of the ball?
a) Upwards
b) Diagonal
c) Projectile motion
d) Vertically downwards
Explanation: The ball moves under the effect of gravity. The direction of acceleration due to gravity is always vertically downwards.
9. A particle in one dimensional motion with zero speed may have non-zero velocity.
a) True
b) False
Explanation: Speed is a magnitude of velocity and the magnitude of non-zero velocity cannot be zero.
10. For a particle in one dimensional motion, which of the following is true?
a) Zero speed at any instant may have zero acceleration at the instant
b) Zero speed may have non-zero velocity
c) Constant speed must have zero acceleration
d) Positive value of acceleration must be speeding up
Explanation: When a particle moves with a constant speed in the same direction, neither the magnitude nor the direction of velocity changes and so acceleration is zero. In case a particle rebounds instantly with the same speed, its acceleration will be infinite which is physically not possible.