Question

1. A 2-kg bowling ball sits on top of a building that is 40 meters tall. (5 pts) Circle one: KE / GPE / both ( can you show work on how you got it) 2. . A 2-kg bowling ball rolls at a speed of 5 m/s on the roof of the building that is 40 tall. (5 pts) Circle one: KE / GPE / both 3.3. A 2-kg bowling ball rolls at a speed of 10 m/s on the ground. (5 pts) Circle one: KE / GPE / both 4. 1. A 1,000-kg car has 50,000 joules of kinetic energy. What is its VELOCITY? 5. 2. A 200-kg boulder has 39,200 joules of gravitational potential energy. What HEIGHT is it at? 6. 3. A 1-kg model airplane has 12.5 joules of kinetic energy and 98 joules of gravitational potential energy. What is its speed? What is its height?

Answer 1

Potential energy is energy due to an object's height above the ground.
Potential energy = mass x gravity x height
Kinetic energy is energy due to the motion of the object.
Kinetic energy = 1/2 x mass x velocity²

1.
The ball is not moving and is at a height above the ground so it has only potential energy.
P.E = 2 x 9.81 x 40
P.E = 784.8 J

2.
The ball is moving and has a height above the Earth's surface so it has both kinetic and potential energy.
P.E = same as part 1 = 784.8 J
K.E = 1/2 x 2 x 5²
K.E = 25 J

3.
The ball has no height above the Earth's surface and is moving so it has only kinetic energy.
K.E = 1/2 x 2 x 10²
K.E = 100 J

4.
50000 = 1/2 x 1000 x v²
v = 10 m/s

5.
39200 = 200 x 9.81 x h
h = 20.0 m

6.
12.5 = 1/2 x 1 x v²
v = 5 m/s
98 = 1 x 9.81 x h
h = 10.0 m