Question

A man of mass 60kg lifts a 15kg mass to a height of 10m in 5 min. his efficiency is

Answer 1

Efficiency = power output /power input × 100%

Power = Work done / Time

Work done = Force × Distance

For power output we have :

15 × 10 × 10 = 1500 Joules

T = 5 × 60 = 300 seconds

Power = 1500/300 = 5

For power input we have.

60 × 10 × 10 = 6000 Joules = work

Power = work/t

Time = 300s

Power = 6000/300 = 20

Efficiency

5/20 × 100 = 25%

Answer 2

GIVEN : MASS OF MAN =60Kg MASS OF A BODY=15Kg

SO TH TOTAL MASS IS 75Kg,HEIGHT OF THE TOWER =10m

TO FIND : EFFICIENCY

X/100.P=W/t=MGH/t=75*10*9.8/5*60= ~ 20%