work and energy
DESCRIPTION
TRANSCRIPT
Work &ENERGY
Energy
• The ability to do work
Work• Using energy to exert a force to
move an object
Work = Energy &
Energy = Work• The work done is equal to the energy
used to do the work.
Calculating Work:
W = 0, if F = 0
W = F d
W = 0, if d = 0
No work done if object doesn’t move.
No work done, whenever there is no force.
Unit: Joule (J) is a Nm
A person pushes with a 110 N force for a distance of 30 m. How much work was done?
Examples:
W = F d
W = ( 110 N ) ( 30 m )
W = 3300 N m
or
W = 3300 J 1 Joule (J) = 1 N m
Potential and Kinetic Energy
Kinetic Energy:
Energy in Motion
Calculating KE:
KE = ½ m v2
KE = 72 J
Example:
What is the KE of 100 kg of water moving at 1.2 m/sec?
KE = 72 ( kg m )/s22
KE = mv2
2
1
KE = ( 100 kg ) ( 1.2 m/s )2
2
1
KE = ( 100 kg ) ( 1.44 m /s )22
2
1
KE = mvKinetic Energy Fact: 2
2
1
The kinetic energy increases dramatically with increasing speed.
35 mi/hr
4 x speed
16 x energy
140 mi/hr70 mi/hr
2 x speed
4 x energy
What is Potential Energy?
oEnergy that is stored and waiting to be used later
What is Potential Energy?
o Potential energy is stored energy
o P.E. = mass x gravity x height
o P.E. = mghDon’t look down,
Rover!Good boy!
Law of Conservation of Energy
• Energy cannot be created or destroyed
• Energy can be transferred from one type or state to another