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 elctric 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 velocity of the car is constant , its acceleration a= 0 . Hence net force on the car F = ma = 0
(e ) As no field ( gravitational /electric /magnetic ) is acting on the elctron , net force on it is zero .