Give the magnitude and direction of the force acting on a stone of mass 0.1 kg (a) just after it is dropped from the window of a stationary train
(b) just after it is dropped from the window of a train running at a constant velocity of `36 km//hr`
(c) just after it is dropped from the window of a train accelerating with `1 ms^(-2)`
(d) lying on the floor of a train which is accelerating with `1 ms^(-2)` the stone being at rest relative to the train .
Neglect the resistance of air throughout .

Explanation

(a) 1 N vertically downwards (b) same as in (a) (c) same as in (a), force at an instant depends on the situation at that instant, not on history. (d) 0.1 N in the direction of motion of the train.