A car is moving with a constant speed on a straight line. What is the net work done by the external force on the car?

A rain drop of radius 2mm falls from a height of 500m above the ground. It falls with decreasing acceleration (due to viscous resistance of the air) until at half its original, height, it attains its maximum (terminal) speed, and moves with uniform speed thereafter. What is the work done by the gravitational force on the drop in the first and second half of its journey? What is the work done by the resistive force in the entire journey if its speed on reaching the ground is 10m s^(-1) ?

A ball moves along a circle under the infulence of centripetal force. What is the work done by the centripetal force on the ball?

The Earth moving round the sun in a circular orbit is acted upon by a force. What is the work done by the force?

What is the optimum speed of the car along the banked road?