Question

A 2 kg rock is released from rest at a height of 29m. ignore

air resistance and determine the kinetic energy,gravitational
potential energy, and total mechanical enerfy at eachof the
followinf heights: 20m; 15m, 5m;9m.

Answer 1

Answer with Explanation:

Mass of rock=2 kg

Height of rock=29 m

Total energy of rocks is equal potential energy at height 29 m due to rest

Total energy of rock=
`mgh`

Where m=Mass of rock

g=
`9.8 ms^(-2)`=Acceleration due to gravity

h=Height of rock

Substitute the values then we get

Total energy of rock=
`2* 9.8* 29=568.4 J`

By conservation law of energy

Total energy 568.4 is equal to mechanical energy at each height.

When rock falls and loses its potential energy and this loss of potential energy convert into kinetic energy at each height.

1.h=20 m

Potential energy=
`2* 20* 9.8=392 J`

Kinetic energy=
`568.4-392=176.4 J`

2.h=15 m

Potential energy=
`2* 15* 9.8=294 J`

Kinetic energy=
`568.4-294=274.4 J`

3.h=5 m

Potential energy=
`2* 5* 9.8=98 J`

Kinetic energy=
`568.4-98=470.4J`

4.h=9 m

Potential energy=
`2* 9* 9.8=176.4 J`

Kinetic energy=
`568.4-176.4=392 J`