Give the magnitude and direction of the net force acting on
(a) a drop of rain falling down with a constant speed
(b) a crok of mass 10 g floating on water
(c) a kit skilfully held stationary in the sky
(d) a car moving with a constant velocity of `30 kh//h` on a rough road
(e) a high speed electron in space for from all gravitational obects and free of electric and magnetic fields.

Explanation

(a) As the rain drop I falling with a constant speed its acceleration a = 0 Hence net force F = ma = 0 (b) As the cork is floating on water its weight is being balanced by the upthrust (equal to weight of water displaced) Hence net force on the cork is zero
(c) As the kite is held stationary net force on the kite is zero in accordance with Newton s first law
(d) Force is being applied to overcome the force of friction But as velocity of the car is constant its acc a = 0 Hence net force on the car F = ma = 0
(e) As no fied (gravitational/electric/magnetic ) is action on the electron net force on it is zero.