Question

An observer inside a windowless train car notices that at one time, a pendulum inside his train car hangs straight down, and at some other time, it is tilted at an angle of 0.5 degrees with respect to the vertical direction. The conductor assumes that someone outside the train is tilting the train car w.r.t. the ground when he sees that the pendulum is tilted. Is there another explanation which does not involve tilting the train?

Answer 1

yes, There are two types of fram of observation (1) Inertial fram (2) Non Inertial fram of reference

The fram which has zero acceceleration is called Inertial fram while the fram which is moving with some acceleration is called Non Inertial fram.

Object present in non inertial fram ( accelerating fram ) experience an pseudo force in opposite direction of acceleration of fram, in given question if train have some acceleration then pendulum would have tilted because of pseudo force.