Question

26. A 40 kg boy jumps from a height of 4m onto a plate-form mounted on springs. As the

spring compress, the plate-form is pushed down a maximum distance of 0.2 cm below its
initial position, and it then rebounds. What is the loss in potential energy by the boy?
a. 800J
b. 1080J
c. 1600J
d. 1680 J​

Answer 1

c. 1600J

Step-by-step explanation:

The loss in potential energy of the boy is given by:

`U=mg \Delta h`

where

m = 40 kg is the mass of the boy

g = 9.8 m/s^2 is the acceleration of gravity

`\Delta h = 4 m + 0.02 m = 4.02 m` is the total change in the height of the boy (4 metres + 2 cm due to the compression of the spring)

Substituting, we find

`\Delta U = (40 kg)(9.8 m/s^2)(4.02 m) = 1577 J \sim 1600 J`