What is the work done by the force of gravity on a satellite moving round the earth? Justify your answer.

What is work done?

What is the work done when the force on the object is zero?

What is the work done by the tension of the string in a simple pendulum?

What is the orbital velocity for a satellite orbiting close to the surface of earth?

‘What is the work done by earth's gravitational force in keeping the moon in its orbit?

Is pi a rational or irrational? Justify your answer.

What is the direction of force of friction acting on a moving object?

What is the S.I. unit of work done?

Deduce the relation between the orbital velocity of a body moving round the earth just over its surface and its escape velocity.

A rain drop of radius 2 mm falls from a height of 500 m 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 10 m s-^1 ?