Physics - NLM Question with Solution | TestHub
A ball is fixed to spring attached to fixed axle at the centre of a rotating wheel. The ball and spring are constrained to move in the groove shown in figure. Two observers one in rotating frame on the ball and one on the ground at rest observe its motion. Platform is rotating with constant angular velocity and spring has attained its stable configuration. Choose the correct statement(s):
Options:(select one or more)
Answer:
Solution:
For the ground observer (inertial frame), the only radial force on the ball is the spring force, directed radially inward; it provides the centripetal force - (A) correct.
For the observer on the rotating platform the ball is at rest; he explains the equilibrium by an outward centrifugal (pseudo) force balancing the inward spring force - (B) correct.
The platform is rotating, hence a non-inertial frame. Newton's first law is not directly applicable to the ball for the platform observer - (C) wrong.
Newton's second law holds only in inertial frames (unless pseudo forces are added), so it is not applicable with respect to both observers - (D) wrong.
Correct options: (A), (B).
