Question

A boy of mass 40kg runs up flight of 50 steps each 10 cm high in 5 sec . Find the work done by the boy , the power developed

Answer 1

work Done can be calculated as

W = F * d
   = m * g * d
  =  40 * 10 * 50 *10
  = 20000
   = 20 K joule
thus 20 K J of work is done by the boy
Power Dissipated can be calculated as

P = W / t
   = 20 /5
   = 4 K Watt

thus power dissipated is 4 KW

Answer 2

Data:
Mass of a boy = m = 40 kg
No. of steps = 50
Height of each step = 10 cm = 0.1 m
Total height = h = 50 x 0.1 = 5 m
Time = t = 5 sec
Work done = W = ?
Power = P = ?
Solution:
Work done = W = m g h
W = (40) (10) (5)    (∵g = 10 m/s²)
W =  2000 J
Power = P = Work done/Time taken
P = W/t = 2000/5
P = 400 W
This is the required answer.