Question

Give the magnitude and direction of the net force acting on a stone of mass 0.1kg.

(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 35km/h.

(c) just after it is dropped from the window of a train accelerating with 1ms-2,

(d) lying on the floor of a train which is accelerating with 1ms-2, the stone being at rest relative to the train. Neglect air resistance throughout.

Answer 1

(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.