4.3: Conservation of Energy

HW 4.3: Conservation of Energy

1. What does the law of conservation of energy state?

Multiple Select

1. What does the law of conservation of energy state? Select all that apply.

• Energy cannot be created or destroyed

• The total energy remains the same

• Energy just changes from one form to another form

• Energy is a valuable resource and should not be wasted

Multiple Choice

2. Does the mechanical energy of an apple falling from a tree change? Explain.

• Yes, the apple experiences a change in motion so mechanical energy changes as well

• No; as the GPE decreases, the kinetic energy increases by the same amount.

  The form of the energy changes, but the total amount of the energy remains the same.

3. What do the arrows in the figures mean?

Open Ended

3) What do the arrows in the figures mean?

4. What does the symbol KE represent in the figure?

Fill in the Blanks

5. Why is kinetic energy at its lowest at the top of the swing?

Open Ended

5. Why is kinetic energy at its lowest at the top of the swing?

3 minute break

remember to look 20 ft away for 20 seconds, giving your eyes a break from the screen

6. Name other items that change electrical energy into thermal energy.

Open Ended

6. Name other items that change electrical energy into thermal energy.

7) What is the 3 step energy transformation involved in running a car engine?

Multiple Choice

What energy is stored in gasoline?

• Chemical Potential Energy

• Thermal Energy

• Kinetic Energy

Multiple Choice

What energy is released when the fuel is ignited and the gases expand?

• Chemical Potential Energy

• Thermal Energy

• Kinetic Energy

Multiple Choice

Now that the expanding gases cause the car to move, what energy is this?

• Chemical Potential Energy

• Thermal Energy

• Kinetic Energy

Multiple Choice

7) What is the 3 step energy transformation involved in running a car engine?

• kinetic --> thermal --> chemical potential

• thermal --> chemical potential --> kinetic

• chemical potential --> thermal --> kinetic

8. Circle the moving parts in the figure. What type of energy is this?

It is KINETIC ENERGY!

Multiple Select

9. How are work and power related? Select all correct answers

• Work and Power have the same units

• Power is the time it takes to do work

• $Power\ =\ \frac{Work}{time}$

Multiple Select

Bonus Q: What are the TWO possible units of power?

• Watts

• Joules

• Joules / second

• Newtons * meters

3 minute break

remember to look 20 ft away for 20 seconds, giving your eyes a break from the screen

ANTICIPATION GUIDES

Multiple Choice

1. Energy can never switch back and forth between kinetic and potential

• True

• False

Multiple Choice

2. As energy changes from one form to another, some of it might be lost/destroyed

• True

• False

Multiple Choice

3. The law of conservation of energy describes what happens to energy as it changes form or is transferred from one object to another

• True

• False

Multiple Choice

4. Mechanical energy is the total amount of potential and kinetic energy in a system

• True

• False

Multiple Choice

5. The total potential energy an apple had before it fell, is NOT the same as the total kinetic energy it had upon hitting the ground (meaning, its total mechanical energy did not remain constant constant

• True

• False

Multiple Choice

6. When riding on a swing, kinetic energy is the lowest at the top of the swing

• True

• False

Multiple Choice

7. When a moving object slows down due to friction, its mechanical energy transforms into thermal energy

• True

• False

Multiple Choice

8. A light bulb transforms electrical to light (and heat) energy

• True

• False

Multiple Choice

9. Cars operate by transforming nuclear energy into kinetic

• True

• False

Multiple Choice

10. Power describes the rate at which energy is used

• True

• False