# Homework Help: Kinetic and Gravitational Energy Related Questions

1. Jul 16, 2011

### NeomiXD

1. A 6.5 kg ball is launched upwards from the ground with a speed of 21 m/s. If all of the ball's kinetic energy is converted to gravitational potential energy, how high will the ball go?

Given:

m = 6.5kg
v = 21m/s
Ek = 1433.25 J
g = 9.8 N/kg [down]

Required:

h =?

Solution:

h = Ek/mg
h = 1433.25 J / (6.5kg)(9.8 N/kg)
h = 22.5m

If all of the ball's kinetic energy is converted to gravitational potential, the ball will go 22.5m high.

2. A 5 kg watermelon is placed on the edge of a balcony 43.0 m high. If all of the gravitational potential energy is converted into kinetic energy after the box is pushed off the balcony, how fast will the watermelon be moving when it hits the ground?

Given:

m = 5 kg
h = 43.0 m
g = 9.8 N/kg [down]
EG = 2107 J

Required:

v =?

Solution:

v = square root 2 EG/ m
v = 2(2107 J)/5 kg
v = 29.03m/s

If all of the gravitational potential energy is converted into kinetic energy after the box is pushed off the balcony, the watermelon would be moving at a speed of 29.03m/s.

So, are my calculations correct?

2. Jul 16, 2011

### Bloodthunder

Yeap.

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