(For simplicity in numerical calculations, take g = 10 m s-2) 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.
(a)
The drop of rain is falling with a constant speed. Therefore, the acceleration of the drop is zero. From Newton’s second law of motion, if the acceleration of the drop is zero thenthe net forceacting on the rain drop will bezero.
(b)
As the cork is floating, the downward weight of the cork is balanced by the upward buoyant force exerted by the water.
Hence, thenet force actingon the floating cork is zero.
(c)
As the kite is stationary, the force exerted by the air is balanced by the tension in the string with which the kite is attached. Hence, there is no net force acting on the kite.
(d)
As the car is moving with a constant velocity,the rate of change of velocity of the car is zero.
From Newton’s second law of motion, if the acceleration of the car is zero then the net forceacting on the carwill be zero.
(e)
The high-speed electron in space is free from the influence of gravity, magnetic and electric fields.
Hence, the net force acting on the electron is zero.
(a)
The drop of rain is falling with a constant speed. Therefore, the acceleration of the drop is zero. From Newton’s second law of motion, if the acceleration of the drop is zero thenthe net forceacting on the rain drop will bezero.
(b)
As the cork is floating, the downward weight of the cork is balanced by the upward buoyant force exerted by the water.
Hence, thenet force actingon the floating cork is zero.
(c)
As the kite is stationary, the force exerted by the air is balanced by the tension in the string with which the kite is attached. Hence, there is no net force acting on the kite.
(d)
As the car is moving with a constant velocity,the rate of change of velocity of the car is zero.
From Newton’s second law of motion, if the acceleration of the car is zero then the net forceacting on the carwill be zero.
(e)
The high-speed electron in space is free from the influence of gravity, magnetic and electric fields.
Hence, the net force acting on the electron is zero.
