Energy
2 TYPES
Kinetic Energy
Potential Energy
Mechanical Energy
 The ability to do work
 Expressed in joules (J)
2 TYPES
Kinetic Energy
Potential Energy
 Energy of motion
Examples include:
•dribbling a
basketball
•a moving vehicle
•a flying bird
 Energy of position or shape
Examples include:
•A basketball sitting
on the floor
•A parked car
•a bird sitting on a
branch
• w = weight
• h = height
• If weight or height
increase then GPE
increases
Potential or Kinetic Energy?
An archer who has
pulled the bow
string back to fire
an arrow. While he
or she is taking aim,
nothing is moving.
Potential Energy
The energy of position or shape!
PE = W x H
Q: How could
we increase
the potential
energy of the
bow?
A: The archer
should pull the
bow back
farther!
(basically
increased the
“height”)
Potential or Kinetic Energy?
A stretched
rubber band.
Potential Energy
The energy of position or shape!
PE = W x H
Q: How could
we increase
the potential
energy of the
rubber band?
A: Stretch the
rubber band
farther!
Potential or Kinetic Energy?
A car driving down
the road.
Kinetic Energy
The energy of motion or movement!
A1: Increase
2
KE = mv /2
the speed of
Q: How could
we increase
the kinetic
energy of the
car?
the car!
Note: Using a
bigger car
would also
increase KE,
but which
would have a
greater effect?
Potential or Kinetic Energy?
A baseball player
waiting patiently at
the plate for the
right pitch.
Potential Energy
The energy of position or shape!
PE = W x H
Q: How could
we increase
the potential
energy of the
bat?
A: Use a
heavier bat!
Potential or Kinetic Energy?
A baseball player
fielding a ground
ball.
Kinetic Energy
The energy of motion or movement!
Q: How could
we increase
the kinetic
energy of the
player? Ball?
A: Increasing
the speed of
the player.
Same with the
ball!
 Total Energy of motion and position of
an object
 ME = KE + PE

PE = KE
 PE = KE
ME
remains
constant!!
 An object can have both PE and KE,
but NOT at the same time!
 Energy Skate Park
• Mechanical energy is the
movement of machine parts.
• Mechanical energy is also
the total amount of kinetic
and potential energy in a
system.
• Wind-up toys, grandfather
clocks, and pogo sticks are
examples of mechanical
energy.
• Wind power uses
mechanical energy to help
create electricity.
Mechanical Energy
=
Potential energy +
Kinetic energy
Potential energy + Kinetic energy = Mechanical energy
Example of
energy changes
in a swing or
pendulum.