NAME PERIOD_____________

PHYSICS GUIDESHEET

ENERGY CONVERSIONS

POTENTIAL AND KINETIC ENERGY

LESSON DESCRIPTION SCORE/POINTS

1. Energy Conversions Worksheet /32

2. Notes on Energy Math (5 pts/side) _____/10

3 foldables – 30 pts each _____/30 ________/72

3. PP 230 – 232 READING GUIDE /13

4. PP 244-253 READING GUIDE /33 ________/46

5. REVIEW QUESTIONS/MATH WS /79 ________/79

6. Review Worksheet (M/C etc) /60 ________/60

Gravitational

Potential Energy = Weight · Height

= Mass · Gravity · Height

GPE = w · h

Gravity

9.8 m/sec2

Weight = Mass · gravity

GPE = m g h

Elastic

Potential Energy = ½ spring constant · distance 2

PE elastic = ½ k d 2

Linear

Kinetic Energy = ½ mass · Velocity 2

KE = ½ m v 2

spring constant = force

distance

k = f

d

Work = Force x distance

Work = F x D

Score _____/32

ENERGY CONVERSIONS WORKSHEET

Fill in one or two examples of Energy listed on the top row being converted into the energy form on the left

column. (Fill in at least 20 boxes for 20 points)

FROM

TO Heat Light Chemical Mechanical Sound Electric

Heat

X

Light

X

Chemical

X

Mechanical

X

Sound

X

Electric

X

In a car, gasoline which is _______________energy is converted to ______________ energy by burning the

fuel. The heated gases expand creating a force that pushes the pistons (this is ________________ energy).

Gears transfer this mechanical energy into movement of the wheels (which is __________________ energy)

Not all of the energy from the exploding gasoline is used to drive the pistons. Some of it just heats the engine.

The moving pistons also create _____________ from friction. Heat energy is taken away from the engine by

the radiator fluid using __________________ (direct contact)

__________________ (fluids moving the heat) and __________________ heat energy going to the atmosphere.

The battery in the car has stored ________________energy. This energy can be turned into

_________________ energy to run the radio, the heater and A/C fans (_______________ energy), run the

headlights, inside lights etc (______________energy) and many other parts. (12 POINTS)

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GRAVITATIONAL POTENTIAL ENERGY NOTES Energy that is stored by lifting it to a higher position. The formula to find GPE is You lift a 50 pound box to a shelf that is 5 feet high. How much work did you do to lift it? How much potential energy is stored in the box? **This shows that the work done to lift the box is stored in the box as potential energy. A 2 kg box is on a shelf 3 meters high. How much potential energy does it have? (gravity = 9.8 m/sec) A 8 kg rock balances on a ledge 50 meters high. Find the gravitational potential energy. (gravity = 9.8 m/sec)

LINEAR KINETIC ENERGY NOTES

The formula to find kinetic energy is: A hammer with a mass of 2 kg is moving 4 meters/sec. How much kinetic energy does it have? If you double the mass to 4 kg, and it still moves 4 m/s, How much kinetic energy? What if you double the speed from 4 meters/sec to 8 meters/sec. The mass is still 2 kg. What is the kinetic energy?

A person and bicycle together have a mass of 600 kg. If they are traveling at 8 meters/sec, how much kinetic energy do they have?

ELASTIC POTENTIAL ENERGY NOTES

When you stretch an elastic or a spring, it wants to return to its unstretched or equilibrium position. The force needed to stretch the spring or elastic depends on: This is called the ___________________________. The letter ______ stands for the spring constant. The formula to find k is: The potential energy stored in a spring or elastic depends on: So the formula to find PE elastic is: When a force of 30 Newtons is applied to a spring, it moves a distance of 0.5 meters. What is the spring constant? How much potential energy is there in a spring that is stretched 0.5 meters, if the spring constant is 60 N/m? How much potential energy is there if you stretch the spring 2 times as far? (1.0 meters) How much potential energy is there if you stretch the spring 3 times as far? (1.5 meters)

Notes: 5 points for each side = 10 points total 3

SECTON 5.1 Reading Guide 230 – 232 1. What is kinetic energy? (1) 2. Write the formula for kinetic energy. (1) 3. The unit for kinetic energy is the same as the unit for what? (1) 4. In SI, kinetic energy is measured in what? (1) 5. What are the English units for energy? (1) 6. Kinetic energy increases _____________________ with the mass. Give an example. (2) 7. Kinetic energy increases with the ______________ of the speed. Give an example (2) 8. Look at Example 5.1 – then solve the following: After a serve, a 0.27 kg volley ball is moving 20 m/s. What is the kinetic energy of the ball? (4 pts: formula, work, answer label) SKIP FROM PAGE 233 TO 244 SECTION 5.2 Reading guide pp. 244 – 253 1. When you toss a ball in the air, you give it __________ energy. (1) 2. At the highest point it stops moving upwards. Its kinetic energy is what? (1) 3. What force causes the ball to stop and then come back down? (1) 4. As the ball rises, it gains the ____________________ to do work. (1) 5. The amount of work the ball can do because of its height above your hand is called what? (1) 6. Write the formula to find gravitational potential energy. (1) 7. What are the units for potential energy in SI and English? (2) 8. In calculation of gravitational potential energy, the height h is measured from what? (1) 9. When you specify a reference level, you are defining the potential energy to be what? (1)

10. An object or fluid has potential energy because of its position in the Earth’s what? (1) 11. It is more accurate to say the ____________________ has potential energy. (1) 12. Explain how the forces of the Earth and an object interact. (2) 13. What is restoring force ? (1) 14. What is elasticity? (1) 15. The elasticity of a spring is due to what? (1) 16. What is the equilibrium position? (1) 17. What happens when you push or pull a spring from the equilibrium position? (1) 18. Most springs exert restoring forces that are what? (1) 19. What happens if you compress or extend a spring past the elastic limit? (1) 20. What does the spring constant tell you? (1) 21. Work is stored in a spring as what? (1) 22. Write the formula to find Elastic Potential Energy (1) 23. Give 4 examples of uses for elastic potential energy. (4) 24. Total energy is not “lost”, it is what? (1) 25. Write the law of conservation of energy. (1) 26. Explain how conservation of energy applies when you toss a ball straight up in the air. (3)

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REVIEW QUESTIONS _______/ 79 POINTS 1. A pile driver hammer stores 100 ft lb of potential energy when the hammer is raised 0.25 ft. How much does the hammer weigh? (show work - 4pts) 2. A system has a total energy of 600 ftlb. If there are no losses of heat, and 250 ftlb is potential energy, describe the amount and type of energy remaining in the system. (2pts) 3. A construction elevator raises a 300 pound load of bricks from the ground to the third floor of the building, 24 feet above the ground. Find the potential energy of the load of bricks when it reaches the third floor. (show work – 4pts) 4. A newspaper printing machine uses a set of rollers to feed paper through the machine. The rollers are held firmly against the paper by a spring. The spring exerts a force of 100 pounds when it is compressed 0.25 feet beyond its upstretched length. a. Find the spring constant (k) that the maintenance technician should specify when ordering a spare replacement. (show work – 4pts) b. Find the amount of potential energy stored in the spring when it is compressed the spring 0.25 feet. (show work – 4pts) 5 . Determine the kinetic energy of a 1000-kg roller coaster car that is moving with a speed of 20.0 m/s. (show work – 4points) 6. If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy? (show work – 4points)

7. Data showing typical ball speeds for different sports: Fill in the kinetic energies of each ball just after it is struck. (6 pts) KE = ½ mv

2

Ball Ball mass Ball velocity KE (J)

(kg) (m/s) before (m/s) after After ball is struck

Tennis ball

0.058

0

51

Squash ball

0.032

0

49

Hand ball

0.061

0

23

Golf ball

0.046

0

69

Football kick

0.42

0

28

Cricket ball

0.16

0

39

(Data taken from : Physics, R. Hutchins, University of BATH, Thomas Nelson & Sons Ltd., 1992) 8. Knowing that the potential energy at the top of the tall platform is 50 J, what is the potential energy at the other positions (A-F) shown on the stair steps and the incline? (Each step is the same height) (8 points) Label on the chart for each step.

Assuming there are NO losses of energy due to friction, when the ball rolls down the incline from the top, or falls straight down the side - what is the Kinetic Energy at the following positions? (4 points) A?_________ C? _________ E? _____________ F?____________

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9. A student does an experiment to see how raising the height of a ramp affects how much potential energy a toy car has at each height, and how much kinetic energy the car has at the bottom of the ramp. The mass of the toy car is 10 kg (remember gravity is 9.8 m/s

2) Fill in the correct energy in the chart below (9pts)

Height in Meters

GPE in Joules (mgh)

Velocity m/s

KE in Joules ½ mv

2

Difference Between GPE and KE

0.25

2 m/s

0.5

3 m/s

1.0

4 m/s

10. The chart shows that not all of the potential energy at the top of the ramp turned into kinetic energy at the bottom of the ramp. Where did the rest of the energy go? (1pt) 11. A person is going bungee jumping off of a tower. Sketch a picture of the bungee jump in the box to the right. (1pt) Identify each of the following on your sketch. (You can draw an arrow pointing to the part of your sketch that fits.) A. Maximum Gravitational Potential Energy (1pt) B. Where you have both GPE and KE (1pt) C. Maximum Elastic Potential Energy (1pt)

12. Classify each of the following according to the type of energy. (1 pt. each – 11 total) 1. Water in a reservoir behind a dam. A. Gravitational Potential

______2. Hydrogen found within the sun. B. Elastic Potential

______3. Batteries for a CD player. C. Chemical Potential

______4. Rock on a cliff . D. Electrostatic Potential

______5. A stretched scale spring. E. Nuclear Potential

______6. A flywheel that is spinning. F. Kinetic Energy

______7. A bungee cord, when the jumper is at the lowest

position, and the cord is stretched

______8. A pendulum at the bottom of its swing.

______9. When positive and negative charges are separated from one

another in a capacitor.

_____10. A skier sliding down a hill.

_____ 11. Rubbing a balloon through your hair, then holding it a few centimeters to

the side of your hair.

Energy converted to Heat can leave a system in three different ways, define each below: and apply to the examples (1pt each) 13. Define Conduction: 14. Define Convection: 15. Define Radiation: MATCHING: Match which type of heat transfer is mostly responsible for each of the following Choose from: A. Conduction B. Convection C. Radiation

_____16. The air near the ceiling is normally warmer than air near the floor.

_____17. You feel the heat from a bonfire even though you are several meters away

from it.

_____18. You can boil water in a microwave oven.

_____19. Smoke rises up a chimney.

_____20. The handle of a metal spoon becomes hot when you use it to stir hot soup.

_____21. Heat lamps over the Pizza’s keep them warm.

_____22. You pound with a hammer on a nail. Both the hammer and the nail get

warm.

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Score __________/60 7

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