Question

The diagram represents the path of a ball that has been thrown upward. Discuss how the kinetic energy (KE), gravitational potential energy (GPE), and total mechanical energy (ME) change between points A (where the ball is thrown from), B (the highest point reached by the ball), and C (where the ball hits the ground). Ignore friction between the ball and the air. (3 points)

Answer 1

Gravitational potential energy:
`GPE_(B)>GPE_(A)>GPE_(C)`

Kinetic energy:
`KE_(B)<KE_(A)<KE_(C)`

Total mechanical energy:
`ME_(A)=ME_(B)=ME_(C)`

Step-by-step explanation:

The gravitational potential energy is directly proportional to height (
`GPE_(B)>GPE_(A)>GPE_(C)`). Since there are no non-conservative forces, the total mechanical energy is conserved (
`ME_(A)=ME_(B)=ME_(C)`) and the total mechanical energy is the sum of gravitational potential and kinetic energies. Then:

`GPE_(A) + KE_(A) = GPE_(B) + KE_(B) = GPE_(C) + KE_(C)` (1)

If we know that
`GPE_(B)>GPE_(A)>GPE_(C)`, then we conclude the following inequation for the kinetic energy:

`KE_(B)<KE_(A)<KE_(C)` (2)