Question

A 110-pound person pulls herself up 4.0 feet. This took her 2.5 seconds. How much power was developed?

0.13 hp
0.32 hp
2.0 hp
3.1 hp

Answer 1

0.32 Hp is the answer. right

Answer 2

Answer: Power developed by her is 0.32 hp

Step-by-step explanation:

Work done , W= Force(F) X Displacement (d) in the direction of force

Thus work done ,
`W=Fd=110* 4.0 ft-lbf = 440 ft-lbf`

Now 1.0 ft-lbf = 1.355 joules of energy

Therefore , work done, W= 440x 1.355 J = 596.2 J

Average Power ,
`P=(work done(W))/(time (t))`

=>
`P=(596.2)/(2.5) watts = 238.5 watts`

We know 746 hp = 1.0 watts

=>
`P=(238.5)/(746) hp=0.32 hp`

Thus average power developed by her is 0.32 hp