Question

A particle stays at rest as seen in a frame. We can conclude that
A. The frame is inertial
B. Resultant force on the particle is zero
C. If the frame may be inertial then the resultant force on the particle is zero.
D. If the frame is non-inertial then there is a non zero resultant force.

Answer 1

Hint: A frame of reference is the set of coordinate systems with time with the help of which the state of rest or of motion of any object with respect to the observer can be known or concluded.

Complete step by step solution:
There are two different types of frame of references: inertial frame of reference and non inertial frame of reference. In the case of an inertial frame of reference, the particle follows Newton’s first law of motion. This means that if no external force is acting it will be at rest.

Since there is no force acting, the resultant force will be zero. On the other hand, if the magnitude of acceleration with which the particle is moving is same as that of frame of reference, in that case the resultant force acting on the particle will not be equal to zero. Then also the particle is said to be at rest.

Hence, if the particle stays at rest as seen in a frame, it can be concluded that if the frame of reference is inertial, the resultant force acting on the particle is zero and if the frame of reference is non-inertial, then there is a non-zero resultant force.

Therefore, Option C and D are correct.

Note: It is important to remember that in case of non inertial frame of reference, Newton’s second law of motion does not hold true. This is because in a non inertial frame of reference, the particle is not in uniform motion.