Download GPE and KE Introduction and Practice Worksheet

Name_____________________________________________
Date__________________
Period_____
SPS7. Students will relate transformations and flow of energy within a system.
a. Identify energy transformations within a system (e.g. lighting of a match)
What is Energy?
Energy and Work:
While work is only done when an object
experiences a change in its motion, energy can
be present in an object or system when nothing
is happening at all. Energy is only observed
when it is transferred from one object to
another.
 Ex: How can you tell when energy is
transferred to an ice cube?
 Both energy and work are measured in
Joules.
Potential Energy:
Potential energy is stored energy due to
position.
Ex: Stretching a rubber band requires work. If
you release a stretched rubber band, it will fly
out of your hand.
 Where is energy “stored” in a rubber
band?
 What are some everyday forms of
“stored” energy?
Gravitational Potential Energy:
GPE depends on both mass and height.
Assuming each of the apples below have the same
mass, which apple has more GPE and why?
A
Calculating GPE:
C
Formula: GPE= mgh
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GPE is measured in
Joules.
(m) Mass is measured in
kg.
(g) gravity= 9.8 m/s2
(h) Height is measured in meters.
Practice Problems:
Calculate the following:
1. a car with a mass of 1200 kg at the top of a 42 m high hill
B
Circle diagram
2. a 65 kg climber on top of Mount Everest (8800 m high)
3. a 0.52 kg bird flying at an altitude of 550 m.
4. A diver has 3400 J of GPE after stepping onto a diving platform that is 6.0 m above water. What is the diver’s
mass in kilograms?
Kinetic Energy
Kinetic energy is energy an object has because of
its motion.
Once one of the apples from our example before
starts to fall, it has the ability to do work. The
potential energy (position) is transformed into
kinetic energy (motion).
 Why does the apple have KE?
Kinetic energy depends on mass and speed.
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An apple can do more work than a cherry falling at
the same speed because an apple has more mass.
Two basketballs are rolling down the court at
different speeds. Which does more work? Why?
Calculating KE
Formula: KE= ½ mv2
 KE is measured in Joules
 (m) Mass is measured in kg.
 (v) Velocity is measured in m/s.
Kinetic energy depends more on speed than on
mass.
Potential Energy vs. Kinetic Energy
The apple has a mass of 20 kg. The tree is 5.1 m high.
What is the GPE?
V= 0 m/s
1000 J of PE
0 J of KE
0
V= 10 m/s
500 J of PE
500 J of KE
0
V= 20 m/s
0 J of PE
1000 J of KE
Other Forms of Energy:
 Mechanical Energy
o The sum of an object’s potential energy and kinetic
energy. ME = KE + PE (gasoline engine)
 Thermal Energy
o The total potential and kinetic energy of all the
microscopic particles in an object. (friction)
 Chemical Energy
o Energy stored in chemical bonds. (food, gasoline)
 Electrical Energy
o Energy associated with electric charges. (lightning)
 Electromagnetic Energy
o A form of energy that travels through space in the
form of waves. (sunlight, x-rays)
 Nuclear Energy
o The energy stored in atomic nuclei. (sun and stars)
 Sound Energy
o Energy that is produced by vibrations of matter and
travels through air or other matter as waves.
(thunder)
0
Calculate the following:
1. What is the kinetic energy of a 44 kg cheetah running at 31 m/s?
Circle diagram
2. Calculate the KE in joules of a 1500 kg car moving at 29 m/s? 18 m/s?
3. A bowling ball traveling 2.0 m/s has 16 J of KE. What is the mass of the bowling ball in kilograms?