A man has power of 90W and mass 60kg runs up a staircase in 40 second. If each step of staircase is 20m high calculate the number of steps

Power is calculated by dividing the work done with the time interval of the motion. Work, on the other hand, is force times the distance traveled. Therefore, we can calculate as follows:

Power=W/t = mgd/t

90 = 60 (9.81) d / 40

d = 6.12 m

Number of steps = 20/6.12 = 3.27 or 3 steps