Download Gravitational Potential Energy = Weight

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NAME
PERIOD_____________
PHYSICS GUIDESHEET
ENERGY CONVERSIONS
POTENTIAL AND KINETIC ENERGY
ACTIVITY
LESSON DESCRIPTION
SCORE/POINTS
1. NT
CLASS OVERHEAD NOTES (5 pts/page)
(Plus 5 pts/page for sample questions)
3 foldables – 30 pts each
/20
______/30
2. TX
PP 230 – 232 READING GUIDE
/31
3. TX
PP 244-253
/39
4. WS
REVIEW QUESTIONS/MATH WS
READING GUIDE
/83
Gravitational
Potential Energy = Weight · Height
= Mass · Gravity · Height
GPE = w · h
Gravity
9.8 m/sec2
GPE = m g h
Elastic
Potential Energy = ½ spring constant · distance
PE elastic = ½ k d 2
Linear
Kinetic Energy = ½ mass · Velocity 2
KE = ½ m v 2
Weight = Mass · gravity
2
spring constant = force
distance
k=f
d
Work = Force x distance
Work = F x D
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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?
Write 5 sample test questions
next to your notes on this side
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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)
Write 5 sample test questions
next to your notes on this side
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SECTON 5.1 Reading Guide 230 – 232
1. What is kinetic energy? (1)
2. Write the formula for kinetic energy and tell what each letter means. (4)
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)
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 and tell what the letters mean. (4)
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)
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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 and tell what the letters mean. (4)
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
_______/ 83 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 block with a mass of 10 kilograms is located 30 meters above a road. If the block fell, what would be its
kinetic energy at the moment it struck the ground? Gravity = 9.8 m/sec 2 (assume no losses from air friction)
(show work - 4pts) (solve for potential energy which converts to kinetic)
3. 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)
4. 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)
5. 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)
6 . 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)
7. 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)
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8.
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 mv2
Ball
Ball mass
(kg)
Tennis ball
Squash ball
Hand ball
Golf ball
Football kick
Cricket ball
0.058
0.032
0.061
0.046
0.42
0.16
Ball velocity
(m/s)
(m/s)
before
after
0
51
0
49
0
23
0
69
0
28
0
39
KE (J)
After ball is
struck
(Data taken from : Physics, R. Hutchins, University of BATH, Thomas Nelson & Sons Ltd., 1992)
9. 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) (12 points)
Label on the chart for each step.
Assuming there are NO losses of energy due to friction, what is the Kinetic Energy at Positions
A?______________ C? _____________ E? _____________ F?__________________
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10. 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/s2)
Fill in the correct energy in the chart below (9pts)
Height in
Meters
GPE in Joules
(mgh)
Velocity
m/s
0.25
2 m/s
0.5
3 m/s
1.0
4 m/s
KE in Joules
2
½ mv
Difference
Between
GPE and KE
11. 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)
12. A person is going bungee jumping off of a tower.
Sketch a picture of the bungee jump 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)
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13. 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)
14. Define Conduction:
15. Define Convection:
16. 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
_____17.
_____18.
_____19.
_____20.
_____21.
_____22.
_____23.
The air near the ceiling is normally warmer than air near the floor.
You feel the heat from a bonfire even though you are several meters away from it.
You can boil water in a microwave oven.
Smoke rises up a chimney.
The handle of a metal spoon becomes hot when you use it to stir hot soup.
Heat lamps over the Pizza’s keep them warm.
You pound with a hammer on a nail. Both the hammer and the nail get warm.