Question

A man whose mass is 80kg climbs a staircase in 20 seconds a expends a power of 120 Watt. Find the height of the staircase​

Answer 1

3.06 m

Step-by-step explanation:

The work done by the man against the gravity is given by

`W=Fh cos\theta` Where F is the force i.e. weight of the man and h is the displacement and
`\theta` is the angle between displacement and force

Since F=mg and
`\theta` is zero

W = mgh

Also, Work=power* time

Therefore, Power*time=mgh

Substituting power for 120 W, time for 20 seconds, g as 9.81 m/s2 and m as 80 Kg

120*20=80*9.81*h and making he the subject of the formula

`h=\frac {120*20}{80*9.81}=3.058103976`

Therefore, the height is approximately 3.06 m