# Potential Energy and Solution

Section 1 Work:

1. A person pulls a toboggan for a distance of 35.0m along the snow. The force in the rope (tension) is 94.0N. How much work is done on the sled?

Solution:

W= Fd W= 94.0N x 35.0m

W= 3290 Nm or J

2. The cable of a large crane applies a force of 2.2x10^4N to a demolition ball as it lifts it vertically a distance of 7.6m. a) How much work is done on the ball? b) Is the work positive or negative? Why?

Solution:

A.) W=( 2.2x10^4N) ( 7.6 m) W= 1.6x10^5 Nm or J

B.) Positive, because the force on the system is positive.

3. When spring arrives a woman packs her winter clothes in a box and lifts it at a constant velocity to the top shelf of her closet, a distance of 1.8m above the floor. If the clothes weigh 150N, how much work is done in lifting them?

Solution:

W= (150N) (1.8M) W= 270Nm or J

4. A luggage carrier is pulled 50.0m with a force of 30.0N, how much work is done on the carrier?

Solution:

W= (30.0N) (50.0m) W= 1500Nm or J

5. You are moving into a new apartment. Your weight is 685N and your belongings have a weight of 915N. How much work does the elevator do in lifting you and your belongings 5 stories (15.2m)?

Solution:

W= (685N+915N) (15.2m) W= (1600N) (15.2m) W= 24,320Nm or J Section 2 Gravitational Potential Energy:

6. A 0.15kg ball is thrown 9.0m straight up. What is the work done by the gravitational force? And what is the change in PE? (Notice anything?)

Solution:

PE= m*a*h PE= (0.15kg) (9.8 m/s^2) (9.0) PE= 13.23 kg m^2/s^2 or J - The change in PE and the calculated on the 1st question are the same. 7. A shot-putter puts a shot (weight 71.1N) that leaves his hand at a distance of 1.52m above the ground. a) Find the work done by gravity when the shot reaches a height of 2.13m. b) Determine the change in potential energy.

Solution:

a.) W=( 71.1N) (2.13m) W= 151.44Nm or J

b.) PE= (71.1N)...

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