1 –A man whose mass is 59 kg, climbs up the stairs in 30sec .If each step is 20cm high ,calculate the power used in climbing the staircase

2—If the electric bulb is of 100watt is lighted up for 2hrs.ho much the electric energy is consumed

3—Find energy in KWhrs consumed in 10hrs  by four devices of power 500W each.

4--- two bodies of equal masses move with uniform velocities v and 3v .find the ratio of their kinetic energies .

5---Explain the transformation of energy in Simple Pendulum. Draw the diagram to show the PE and KE points  and the transformations .

The power in thsi case would be potential energy acquired by the man divided by time taken.

Potential energy = mgh  (here h if the total height, which is an unknown)

time = 30 s

so P = mgh/30

You can use the standard power-energy relation for questions  (2) and (3)

P= E/t  P is in KiloWatts, E is in KiloWatthour and t is in hours

We know that,

KE = (1/2)mv²

so,

KE1 = (1/2)mv1²

and KE2 = (1/2)mv2²

where v1 = v

and v2 = 3v

so,

KE1/KE2 = 1/9

The KE and PE in a simple pendulum are inversely proportional to each. Firs PE is max and starts to decrease the KE which was zero starts to increase at the same time.