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

Answer:

Gravitational potential energy: $GPE_{B}>GPE_{A}>GPE_{C}$

Kinetic energy: $KE_{B}$

Total mechanical energy: $ME_{A}=ME_{B}=ME_{C}$

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:

$KE_{B}$ (2)