Question

Acceleration of a body can be zero when
A. No force is acting on it.
B. One force of infinite magnitude is acting on it.
C. Multiple forces are acting on it.
D. Can never be zero.

Answer 1

Hint: This question has multiple correct answers. Recall Newton’s laws of motion to answer this question. If the multiple forces act on the body, they can be cancelled out if they have equal magnitudes and opposite directions.

Complete answer:
To answer this question, we need to discuss Newton’s laws of motion. We know that Newton’s first law states that the body in the motion stays in the motion until and unless it is acted upon by an external force to change its direction. Also, the body in the rest position stays in the rest position unless and until applied force is not applied to move it.
We also know Newton’s second law of motion which states that the acceleration produced in the body is proportional to the applied force which produces the acceleration.
To answer this question, let’s check every option one by one as follows,
We have according to Newton’s second law of motion,
\[{F_{net}} = ma\], where, m is the mass of the body and a is the acceleration.
When no force acts on the body, from the above equation, the acceleration of the body must be zero. Therefore, the option (A) is correct.
If a single force of infinite magnitude acts on the body, we can say that the body must be accelerating according to Newton’s second law of motion. Therefore, the option (B) is correct.
If we have two forces of the same magnitude but in the opposite direction acts on the body, these forces will cancel out and the net force on the body will be zero. Therefore, according to Newton’s second law of motion, we can say that the acceleration of the body must be zero. So, the option (C) is correct.
If we have the body moving in the uniform motion, its velocity does not change with time. In that case the acceleration of the body becomes zero. Therefore, the option (D) is incorrect.

So, the correct answer is option (A), (B), and (C).

Note:
Newton’s second law of motion can also be stated as the change in the linear momentum with respect to time of the body is equal to the force acting on the body to change its velocity. Therefore, \[F = \dfrac{{dP}}{{dt}}\]. Students can use this equation to answer this question. If the body does not undergo change in linear momentum with respect to time, the force acting on it is zero