Question

A person is sitting in a train which is moving with an acceleration of 10 m/$s^2$ rightwards. A pendulum is hanging from the ceiling

(P) Draw the Free Body Diagram of the bob with respect to the person sitting in the train.

(Q) Draw the same with respect to a person who's standing outside.

• A. P - (II); Q - (IV)
• B. P - (I); Q - (IV)
• C. P - (II); Q - (III)
• D. P - (I); Q - (III)

Answer 1

The correct option is A

P - (II); Q - (IV)

The man is in the train's frame

Since train is accelerating so it's non-inertial

Clearly the ball has tension and mg.But the ball is at rest with respect to the man in the train so it should be in equilibrium.

i.e.$\sum F=0$

This cannot result in

$\sum F=0$
So inclusion of pseudo acceleration gives the F.B.D w.r.to the person in the train