Energy

1
Energy

• Chapter 9 Section 4

2
Energy

• Energy is the ability to do work or cause change
• What is Transfer of Energy?
• When an object or living thing does work on
  another object, some of its energy is transferred
  to that second object.
• When energy is transferred, the object upon which
  work is done gains energy.
• The SI Unit for both Work Energy Joule

3
A moving object, such as wind, can do work when
it strikes another object and moves it some
distance.When a breeze does work lifting leaves,
it transfers energy to them.
4
Kinetic Energy

• What is Kinetic Energy?
• Energy an object has due to its motion
• Depends on the objects MASS and its SPEED
• Kinetic energy increases as mass increases or if
  its speed increases.
• Kinetic Energy ½ Mass x Speed2

5
BRAIN BREAK!

• With your partner, create an analogy for Kinetic
  Energy and how mass and speed are related.

6
Potential Energy

• Stored energy that results from the position or
  shape of an object.
• Object has the potential to do work.

7

• 1) Gravitational Potential Energy
• Related to an objects height.
• GPE Weight x Height
• Does a skier have more gravitational potential
  energy on a 50 meter high jump or a 40 meter high
  jump?
• What is the GPE of a skier that weighs 500
  Newtons and is on a 40 meter high ski jump?

8

• 2) Elastic Potential Energy
• When an object gains Potential energy because it
  is stretched or squeezed.
• What are some examples?
• Archer pulling back on an arrow changes the shape
  of the bowthe bow now has more potential energy
  that can be used to send the arrow flying

9
Mechanical Energy

• An objects combined kinetic energy and potential
  energy
• Mechanical Energy
• Kinetic Energy Potential Energy

10

• For example
• A football weighs 4 Newtons and has a mass of .4
  kg
• What is the footballs Kinetic Energy if it is
  moving at a speed of 14 m/s?
• Kinetic Energy ½ Mass x Speed2
• 39 Joules
• What is the footballs Potential Energy if it is
  3 meters above the ground?
• Potential Energy Weight x Height
• 12 Joules
• What is the footballs mechanical energy?

11
Transformation between Potential Kinetic Energy

• An object that rises or falls experiences a
  change in its kinetic and gravitational potential
  energy.
• Active Art Textbook Link
• http//www.phschool.com/atschool/phsciexp/energy_t
  ransformations/index.html

12
The Kinetic Energy of the ball thrown into the
air becomes gravitational potential energy. Its
potential energy becomes kinetic energy as it
falls.