A boy weighing 40 kgf climbs up a stair of 30 steps, each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes.

Compare :

(i) the work done by them, and

(ii) the power developed by them. Take g = 10 N kg^-1.

A man raises a box of mass 50kg to a height of 2m in 20s, while another man raises the same box to the same height in 50s.

(a) Compare: (i) the work done, (ii) the power developed by them.

(b) Calculate the (i) the work done, (ii) the power developed by each man.

Take g = 10N kg^-1.

A body of mass 5 kg moves along a straight line under the action of a variable force. From x = 0 to x = 4 m, the force acts in the direction of displacement and increases linearly from 0 N to 20 N. From x = 4 m to x = 6 m, the motion of the body reverses while the force acts in forward direction. From x = 6 m to x = 10 m, the force becomes negative acting opposite to the original direction of motion. Calculate the net work done by the force on the body.

According to the work energy theorem, the increase in the kinetic energy of a moving body is equal to …………… by a force acting in the direction of the moving body.

1. displacement
2. velocity
3. acceleration
4. work done