Download Potential Energy

Name: _______________________________________
Physical Science – Ch. 4 and 5
Energy Notes:
BASICS:
Energy is the ability to_________ ___ __________ or do _______.
Work is the ________________________________________________________________________
The FORCE must be in the _____________________ direction as the direction the object moves.
Is work being done in the following examples?
Lift a book one meter
Walking around the classroom with a book.
In which case is more work being done? Explain
Lift one book up 1 m or 2 books .5 m
The abbreviation for energy is _____.
The SI unit of measurement for energy is (the same as the unit for work) the ______________.
There are different FORMS of energy: List a few below:
1. ___________________________
2. ____________________________
3. ____________________________
ANALOGY:
A______________analogy can be used when learning about energy.
Energy can change _________, but energy from the Sun that warms you and energy from the food you eat are
just different forms of the _________thing – energy.
TWO MAIN TYPES OF ENERGY:
1. _______________Energy –_________ energy due to position
2. ________________Energy – the energy of ______________
Potential energy:
I.
II.
______________ _________(PE) = energy stored in an object due to its ___________,
which means the object has potential to do _______
Examples: stretched or compressed _______
stretched ___________ band
drawn _______& _______
chemical, _____________, magnetic
_____________PE = energy stored in an object due to its position __________ ____ ______
Examples: toy at ________ of staircase or an apple on a ___________
Calculate potential energy:
Potential Energy = mass X acceleration due to _______X _______from ground
PE = mgh (unit is Joules = J)
Practice Problem: what is the gravitational potential energy of the 3kg star if it is 3m off the ground? _____ J
3m
Equation: ______________
Show your work:
Name: _______________________________________
Physical Science – Ch. 4 and 5
Kinetic energy:
Kinetic energy = energy due to _______ ( examples: riding a _______, moving _____________)
Calculate Kinetic energy:
Kinetic Energy = ½ _______X _______
KE = ½ mv2 (unit is Joules = J)
Practice Problems:
1.
What is the KE of a 10kg cat moving at 10m/s? __________ J
2.
What is the KE of a 20kg dog moving at 10m/s? __________ J
3.
What would the dog’s KE be if it was moving at 20m/s? __________ J
Something that has twice the _______will have _______as much KE
Something that is twice as _______will have _______times as much KE because velocity is _______
Mechanical energy:
____________Energy = sum of _______ and _______ of a system (Ac _______object has PE due to
its ____________above ground and has KE due to _________ of the falling object.)
Non-Mechanical energy:
_______________________Energy = energy at the _______level…doesn’t affect _______
(examples: food, _______reactions, sun)
CLASSWORK / HOMEWORK:

Read over notes and make sure you have filled in all of the blanks

Practice calculating KE and PE (complete Practice problems ws #1 and ws#2)
PART 4: CONSERVATION OF ENERGY
Name: _______________________________________
Physical Science – Ch. 4 and 5
I. Transformation of energy = easily
seen on rollercoaster
•
of hill = no KE and all PE
Transformation
• of
PE_______from
becomes KE asone
cartype
goesto another is easily seen
a. Top of hill• = bottom
no _______
of hilland
= noall
PE_______
and all KE
• KE
as car
cargoes
goes _______
, but PE
b. PE becomes
KE as
How
is energy
transferred
as ball is
c. Bottom of•hill
= all
_______
no _______
thrownas
into
(p.308)
d. _______ decreases
carair?
goes
uphill, but _______ increases
Conservation of Energy
I.
on a _______
II.
Law of Conservation of _______= energy cannot be _______or _______; it only changes
_______(energy examples: solar, electrical, _______, light, chemical, mechanical, _______, water,
muscle, _______)
SUN is _______ source of _______
III.
_______of machines = compares work _______to work _______…never 100% due to _______
Three types of friction are:
1. sliding = two flat _____________________ rubbing against each other
2. fluid = movement through a ______________, which can be a liquid or gas, this includes ____ resistance
3. rolling = results from ____________ between two surfaces, one of which is ______________
usefulwork
output
Efficiency

X
100
%
usefulwork
input
(example: it takes 1800J of work to push a piano up a ramp, but due to ramp friction, you must actually exert
2400J of work What is the ramp’s efficiency? ____________J
Name: _______________________________________
Physical Science – Ch. 4 and 5
Practice Problems ws #1:
Conceptual practice:
1. Two books with different masses fall off the same bookshelf. As they fall, which has more kinetic
energy and why?
2. How can the gravitational potential energy of an object be changed?
3. Compare and contrast potential and kinetic energy.
4. Compare and contrast elastic potential energy, chemical potential energy and gravitational potential
energy.
5. A car is lifted a certain distance in a service station and therefore has PE with respect to
the floor. If it were lifted twice as high, how much PE would it have? (Hint: PE = mgh)
6. Two cars are lifted to the same elevation at a service station. If one car is twice as heavy as the other,
how do their PE compare?
7. Find the PE and KE of the object as it is falling to the ground:
PE = 100J
KE = 0 J_
PE = _____
KE = 25 J_
PE = _____
KE = _____
PE = 75 J
KE = _____
PE = 0J
KE = _____
Top – Max. = PE
Bottom – Max. KE
Practice #1: Calculating Kinetic and Potential Energy
8.
An 80 kg diver jumps off a 10 m platform. Calculate how much gravitational potential energy the
diver has at the top of the platform and halfway down.
9. A 0.06 kg tennis ball starts to fall from a height of 2.9 m. How much gravitational potential energy
does the ball have at that height?
10. What is the KE of a 3kg box tossed across the yard at 5m/s?
11. What is the KE of a 40kg track and field girl running at 7m/s? What about a 40kg boy running
35m/s?
Name: _______________________________________
Physical Science – Ch. 4 and 5
Homework – Practice ws #2: Calculating Kinetic and Potential Energy
Kinetic Energy
Use this equation: KE = ½ mv2
1. What is the kinetic energy of a truck with a mass of 800 kg and a speed of 10 m/s?
2. What is the kinetic energy of a skateboarder with a mass of 70 kg and a speed of 5 m/s?
3. What is the kinetic energy of a skier with a mass of 80 kg and a speed of 15 m/s?
4. What is the mass of an object with a speed of 30 m/s and a kinetic energy of 400 J?
5. A car with KE of 6250 J and a mass of 500 kg is traveling at what velocity?
Gravitational Potential Energy
Use this equation: GPE = mgh or GPE = m x 10 m/s2 x h
6. What is the GPE of a bowling ball with a mass of 1.5 kg and held 2 meters above the ground?
7. What is the GPE of a vase with a mass of 0.05 kg and a height of 3.4 meters above the ground?
8. A cat jumps to the top of a 5.5 m shelf and now has 50 J of energy. What is the mass of the cat?
9. The GPE of a ball is 50 J. It has a mass of 0.5 kg. What is the height in meter it was dropped from
above the ground?
10. What is the GPE of a person standing at the top of a ladder with a height of 15 meters? The person
has a mass of 80 kg.