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Unit VII: Worksheet 3a (Ei + ΔE = Ef)

For each situation shown below:

1. Show your choice of system in the energy flow diagram, unless it is specified for you.

**Always include the earth in your system.

2. Decide if your system is frictionless or not, and state this.

3. Sketch an energy bar graph for the initial situation.

4. Then complete the analysis by showing energy transfers and the final energy bar graph.

1.

2.

3.

4. A person pushes a car, with the parking brake on, up a hill. (person not in system)

5. A load of bricks rests on a tightly coiled spring, then is launched into the air.

6. A crate is propelled up a hill by a tightly coiled spring.

7. A bungee jumper falls off the platform and reaches the limit of stretch of the cord.

8. An elevator, initially moving downward, is brought to rest on the ground floor.

9. Create your own situation and construct corresponding energy bar graphs and system schema.

System = ______________________

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Edis

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

yo>0

vo>0

y = 0

v = 0

system

boundary

0

y

Edis

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

v = 0

Initial

0

y

Final

Edis

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

Edis

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

vo=0

yo=0

Final

v>0

0

y

0

Friction present

”E= 0 J

ΔE= 0 J

Friction present

ΔE= 0 J

vo=0

yo=0

Frictionless

ΔE= 0 J

vo=0

yo=0

v = 0

y > 0

frictionless

0

y

Edis

Eel

Initial

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

Initial

Final

y

v>0

Friction present

ΔE≠ 0 J

Friction present

ΔE= 0 J

Final

Initial

Edis

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

vo>0

yo=0

v = 0

y > 0

0

y

Edis

ΔE= 0 J

ΔE= 0 J

Edis

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

Final

frictionless

Edis

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

Eel

Eg

EK

Final

0

Eg

Initial

Eel

EK

0

Energy Flow

Diagram

Friction present

ΔE≠ 0 J

-3 units

+4 units

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