3) A 100kg man runs up a staircase
3 cm high in 5 seconds. How much
pouwer does he develop?

Power = 5.88 Watt

Explanation:

Mechanical Work and Power

Mechanical work is the amount of energy transferred by a force. Its SI unit is the joule.

Being  the force vector and  the displacement vector, the work is calculated as:

If both the force and displacement are parallel, then we can use the equivalent scalar formula:

Power is the amount of energy transferred or converted per unit of time. In the SI, the unit of power is the watt, equal to one joule per second.

The power can be calculated as:

Where W is the work and t is the time.

The m=100 Kg man goes up a distance of s=3 cm = 0.03 m in t=5 seconds. To calculate the work done against gravity the weight is considered as the force:

F = m.g = 100*9.8

F = 980 N

The work is:

W = 980*0.03

W = 29.4 J

Finally, the power is:

P = 5.88 Watt