Download Mechanical Energy

Energy
Is all around you
Physical Science
Studying the interaction between
matter and energy
Nature of Science
• You hear energy as sound, you see energy as light,
you can feel energy in wind.
• Living organisms need energy for growth and
movement.
• You use energy when you hit a tennis ball, lift a
grocery bag, or compress a spring.
• Energy is the ability to do work
and work is the transfer of energy.
Forms of Energy
• Energy appears in many
forms. The following are
some forms of energy:
• Mechanical
• Heat
• Chemical
• Electrical
• Sound
• Light
• Nuclear
Mechanical Energy
• Energy possessed by
an object due to its
motion or stored
because of its position.
• Two types of
mechanical energy:
– Kinetic energy
– Potential energy
• Units  Joules
Mechanical Energy
Kinetic Energy - Energy
due to the motion of a
body
KE = ½
2
mv
velocity (m/s)
Kinetic Energy (J)
mass (kg)
“If you ain’t first, you’re last”
claims famed race car driver
Ricky Bobby. If Ricky’s 720
kg car has 4,844,000 J of
kinetic energy, how fast does
he go to keep in first place?
Mechanical Energy
Potential Energy - Stored energy because of
relative position between interacting bodies.
Potential Energy
Acceleration due to gravity
PE = mgh
height (m)
Potential Energy (J)
mass (kg)
• The Millenium Park fountain in
Chicago appears to have water
spitting from the mouth of a
Chicago citizen. If 500 kg of
water spray out of the fountain
and carries 12,000 J of
gravitational potential energy,
how high does the water spray
from?
What type of mechanical energy do
the blocks have?
Potential
Energy
Both
Potential
and
Kinetic
Kinetic
Energy
Law of Conservation of Energy
• Energy cannot be created nor destroyed.
• Total energy before = total energy after
• KEi + PEi = KEf + PEf