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## Bellringer

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### For example, sunlight is the ultimate source of energy on Earth. Look at the illustration below, and identify the types of energy involved. Bellringer, ... – PowerPoint PPT presentation

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Title: Bellringer

1
Bellringer
• You should already have learned that energy is
always conserved. Instead of being created or
destroyed, energy just changes from one form to
another. For example, sunlight is the ultimate
source of energy on Earth. Look at the
illustration below, and identify the types of
energy involved.

2
Bellringer, continued
• How does sunlight provide the energy the girl
needs to swing the bat? (Hint What do you need
to have energy?)
• 2. When the girl hits the ball, she exerts a
force on it. Does she do work on the ball in the
scientific sense of the term? Explain your
• 3. After the girl hits the ball, the ball moves
very fast and has energy. When the ball hits the
fielders glove, it stops moving. Given that
energy can never be destroyed but merely changes
form, what happens to the energy the ball once
had? (Hint If you are the fielder, what do you
hear and feel as you catch the ball?)

3
Energy and Work
• What is the relationship between energy and work?

4
13-3-1 Energy and Work
• Whenever work is done, energy is transformed or
is transferred from one system to another system.

5
13-3-2 Energy and Work
• energy the capacity to do work
• Energy is measured in joules (J).

6
Potential Energy
• Why is potential energy called energy of
position?

7
13-3-4 Potential Energy
• potential energy the energy that an object has
because of the position, shape, or condition of
the object

8
13-3-5 Potential Energy, continued
• Any object that is stretched or compressed to
increase or decrease the distance between its
parts has elastic potential energy.

9
13-3-6 Potential Energy, continued
• Examples stretched bungee cords, compressed
springs

10
13-3-7 Potential Energy, continued
• Any system of two or more objects separated by a
vertical distance has gravitational potential
energy.

11
13-3-8 Potential Energy, continued
• Example a roller coaster at the top of a hill

12
13-3-9 Potential Energy, continued
• Gravitational potential energy depends on both
mass and height.
• .

13
13-3-10 Potential Energy, continued
• grav. PE mass ? free-fall acceleration ?
height,
• or PE mgh

14
13-3-11Math Skills
• Gravitational Potential Energy
• A 65 kg rock climber ascends a cliff. What is
the climbers gravitational potential energy at a
point 35 m above the base of the cliff?
• 1. List the given and unknown values.
• Given mass, m 65 kg
• height, h 35 m
• free-fall acceleration, g 9.8 m/s2
• Unknown gravitational potential energy, PE ? J

15
13-3-12 Math Skills, continued
• 2. Write the equation for gravitational potential
energy.

PE mgh 3. Insert the known values into the
equation, and solve.
PE (65 kg)(9.8 m/s2)(35 m) PE 2.2 ? 104
kgm2/s2 PE 2.2 ? 104 J
16
Kinetic Energy
• What factors does kinetic energy depend on?

17
13-3-13 Kinetic Energy
• Kinetic energy depends on both the mass and the
speed of an object.

18
13-3-14 Kinetic Energy
• kinetic energy the energy of an object due to
the objects motion

19
13-3-15 Kinetic Energy
• KE
• ½ ? mass ? speed squared,
• or KE ½mv2

20
Kinetic Energy, continued
• Kinetic energy depends on speed more than mass.

21
Kinetic Energy, continued
• Atoms and molecules have kinetic energy.

22
13-3-18 Other Forms of Energy
• mechanical
• chemical
• nuclear
• electrical
• solar
• light
• sound