A boy of mass 40 kg runs up a flight of 15 steps each 15 cm high in 10

1.	A boy of mass 40 kg runs up a flight of 15 steps each 15 cm high in 10 s. Find:(i) the work done and(ii) the power developed by himTake g = 10 N kg-1
Answer» Force of gravity on boy F= mg = 40 × 10 = 400N Total distance covered in 15 steps , S = 15 × 15cm = 225cm = 2.25m Work done by the boy in climbing = Force x distance moved in direction of force Work, W = F × S = 400 × 2.25 = 900J Power developed = work done/time takrn = 900J/10s = 90W

A boy of mass 40 kg runs up a flight of 15 steps each 15 cm high in 10 s. Find:(i) the work done and(ii) the power developed by himTake g = 10 N kg-1

Answer»

Force of gravity on boy

F= mg = 40 × 10 = 400N

Total distance covered in 15 steps ,

S = 15 × 15cm = 225cm = 2.25m

Work done by the boy in climbing = Force x distance moved in direction of force

Work, W = F × S = 400 × 2.25 = 900J

Power developed = work done/time takrn = 900J/10s = 90W