Give the magnitude and direction of the net force acting on
(a) a drop of rain falling down with a constant speed
(b)a cork of mass 10 g floating on water
(c) a kite skillfully held stationary in the sky
(d) a car moving with a constant velocity of `30 km//h ` on a rough road
(e) a high-speed electron in space far from all material objects and free of electric and magnetic fields.

Explanation

(a) As the rain drop is 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 velocty of the car is constant , its acceleration . a=0. Hence net force on the car F=ma=0.
(e) As no field (graveitational //electric//magnetic ) is acting on the electron , net force on it is zero.