Energy Model Worksheet2 BarGraphs - Modeling Physics

<strong>Energy</strong> <strong>Model</strong> Worksheet 2<br />

Qualitative <strong>Energy</strong> Storage and Conservation with Bar Graphs<br />

For each situation shown below:<br />

1. List objects in the system within the circle. **Always include the earth’s gravitational field in your system.<br />

2. On the physical diagram, indicate your choice of zero height for measuring gravitational energy.<br />

3. Sketch the energy bar graph for position A, indicate any energy flow into or out of the system from position A to<br />

position B on the System/Flow diagram, and sketch the energy bar graph for position B.<br />

4. Write a qualitative energy equation that indicates the initial, transferred, and final energy of your system.<br />

1a. In the situation shown below, a spring launches a roller coaster cart from rest on a<br />

frictionless track into a vertical loop. Assume the system consists of the cart, the earth, the<br />

track, and the spring,<br />

B<br />

Position A<br />

System/Flow<br />

Position B<br />

A<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

E k E g E e E k E g E e E diss<br />

1b. Repeat problem 1a for a frictionless system that includes the cart, the earth, and the track,<br />

but not the spring.<br />

B<br />

Position A<br />

System/Flow<br />

Position B<br />

A<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

E k E g E e E k E g E e E diss<br />

1c. Use the same system as problem 1a, but assume that there is friction between the cart and<br />

the track.<br />

B<br />

Position A<br />

System/Flow<br />

Position B<br />

A<br />

E k E g E e E k E g E e E diss<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

©<strong>Model</strong>ing Workshop Project 2006/STL Group-R. Rice 1 JBS version 2010, v1.1

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1d. This situation is the same as problem 1a except that the final position of the cart is lower on<br />

the track. Make sure your bars are scaled consistently between problem 1 and 4. Assume<br />

the system consists of the cart, the earth, the track, and the spring.<br />

Position A<br />

System/Flow<br />

Position B<br />

A<br />

B<br />

E k E g E e E k E g E e E diss<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

2a. A moving car rolls up a hill until it stops. Do this problem for a system that consists of the<br />

car, the road, and the earth. Assume that the engine is turned off, the car is in neutral, and<br />

there is no friction.<br />

y<br />

A<br />

B<br />

y B > 0<br />

v B = 0<br />

Position A<br />

System/Flow<br />

Position B<br />

y A = 0<br />

v A > 0<br />

E k E g E e E k E g E e E diss<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

2b. Repeat problem 2a for the same system with friction.<br />

y<br />

A<br />

B<br />

y B > 0<br />

v B = 0<br />

Position A<br />

System/Flow<br />

Position B<br />

y A = 0<br />

v A > 0<br />

E k E g E e E k E g E e E diss<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

3a. A person pushes a car, with the parking brake on, up a hill. Assume a system that includes<br />

the car, the road, and the earth, but does not include the person.<br />

y<br />

A<br />

B<br />

h B > 0<br />

v B = 0<br />

Position A<br />

System/Flow<br />

Position B<br />

h A = 0<br />

v A = 0<br />

E k E g E e E k E g E e E diss<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

©<strong>Model</strong>ing Workshop Project 2006/A TIME for PHYSICS FIRST 2 JBS version 2010 v1.1

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3b. Repeat problem 3a for a system that includes the person.<br />

y<br />

Position A<br />

B<br />

System/Flow<br />

Position B<br />

A<br />

h B > 0<br />

v B = 0<br />

h A = 0<br />

v A = 0<br />

E k E g E e E k E g E e E diss<br />

Qualitative <strong>Energy</strong> Conservation Equation:<br />

4a. A load of bricks rests on a tightly coiled spring and is then launched into the air. Assume a<br />

system that includes the spring, the bricks and the earth. Do this problem without friction.<br />

B<br />

y<br />

h B > 0<br />

v B > 0<br />

Position A<br />

System/Flow<br />

Position B<br />

A<br />

h A = 0<br />

v A = 0<br />

<strong>Energy</strong><br />

Equation:<br />

E k E g E e E k E g E e E diss<br />

4b. Repeat problem 4a with friction.<br />

B<br />

y<br />

h B > 0<br />

v B > 0<br />

Position A<br />

System/Flow<br />

Position B<br />

A<br />

h A = 0<br />

v A = 0<br />

<strong>Energy</strong><br />

Equation:<br />

E k E g E e E k E g E e E diss<br />

4c. Repeat problem 4a for a system that does not include the spring.<br />

B<br />

y<br />

h B > 0<br />

v B > 0<br />

Position A<br />

System/Flow<br />

Position B<br />

A<br />

h A = 0<br />

v A = 0<br />

<strong>Energy</strong><br />

Equation:<br />

E k E g E e E k E g E e E diss<br />

©<strong>Model</strong>ing Workshop Project 2006/A TIME for PHYSICS FIRST 3 JBS version 2010 v1.1

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5a. A crate is propelled up a hill by a tightly coiled spring. Analyze this situation for a<br />

frictionless system that includes the spring, the hill, the crate, and the earth.<br />

y<br />

Position A<br />

System/Flow<br />

Position B<br />

B<br />

h B > 0<br />

v B > 0<br />

0<br />

A<br />

h A = 0<br />

v A = 0<br />

<strong>Energy</strong><br />

Equation:<br />

E k E g E e E k E g E e E diss<br />

5b. Repeat problem 5a for a system that does not include the spring and does have friction.<br />

y<br />

Position A<br />

System/Flow<br />

Position B<br />

B<br />

h B > 0<br />

v B > 0<br />

0<br />

6a. A bungee jumper falls off the platform and reaches the limit of stretch of the cord. Analyze<br />

this situation for a frictionless system that consists of the jumper, the earth, and the cord.<br />

y<br />

A<br />

A<br />

h A = 0<br />

v A = 0<br />

h A > 0<br />

v A = 0<br />

y<br />

<strong>Energy</strong><br />

Equation:<br />

E k E g E e E k E g E e E diss<br />

Position A<br />

System/Flow<br />

Position B<br />

0<br />

0<br />

B<br />

B<br />

h B > 0<br />

v B = 0<br />

E k E g E e E k E g E e E diss<br />

6b. Repeat problem 6a if the cord is not part of the system.<br />

y<br />

A<br />

h A > 0<br />

v A = 0<br />

y<br />

Position A<br />

System/Flow<br />

Position B<br />

0<br />

0<br />

B<br />

B<br />

h B > 0<br />

v B = 0<br />

E k E g E e E k E g E e E diss<br />

©<strong>Model</strong>ing Workshop Project 2006/A TIME for PHYSICS FIRST 4 JBS version 2010 v1.1