Inside a railcar there hangs a lightweight pendulum bob from the ceiling
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
Inside a railcar there hangs a lightweight pendulum bob from the ceiling. When the car is at rest at the station, the pendulum string hangs vertically. After departure the train accelerates uniformly along a straight, level track, and the pendulum string is observed by passengers to settle at a constant angle of 12° from the vertical toward the rear of the car. Air resistance on the bob is negligible.
(a) Describe qualitatively what an observer standing on the ground beside the track sees the pendulum bob do while the railcar is accelerating.
(b) Determine the magnitude of the train’s acceleration using the observed 12° string deflection. Show your reasoning clearly.
(c) Explain whether the passenger’s reference frame inside the accelerating railcar satisfies the conditions of an inertial frame. Support your conclusion with specific evidence from parts (a) and (b).