Question

If a body does not change its position with respect to its surroundings, the body is said to be_______
A). At rest
B). In motion
C). In free fall
D). None of these

Answer 1

Hint: Speed is a scalar quantity while velocity is a vector quantity. Velocity depends on the direction. Speed is independent of direction. Speed means the distance upon a time in no particular direction. The rate of change of distance in a particular direction is called velocity.

Complete step-by-step solution:
A body is said to be in motion when its position continuously changes concerning time.
The body is not in motion when the average speed is zero. Also when the position doesn’t change with time, the body is said to be at rest.
Hence, option A is correct.
Additional Information:
When a body is in motion, it moves in a straight line with constant velocity thus covering the equal distance in equal interval of time irrespective of the duration of time is called uniform motion.
When a body is in motion, it moves in different directions with changing velocities thus covering different distances in different intervals of time, irrespective of the time interval duration is called non-uniform motion.
Acceleration of a body is non-zero only if it moves with varied velocity over a given interval of time.

Note: Students usually get confused between uniform acceleration and uniform motion. Uniform acceleration leads to non-uniform velocity and is not the same. A body travels with a constant velocity in uniform motion. A body travels with a constant increase or decrease in velocity when it is in uniform acceleration. Students might think the above statement is false if they think of speed and velocity to be the same but they differ based on direction.