Transcript to the Power Point on Energy

Work, Power, Energy
Words to define:
Work
Joule
Power
Watt
Energy
Kinetic Energy
Potential Energy
Machine
Fulcrum
Pulley
Law of Conservation of Energy
Work - amount of energy gained or lost
by an object when a force moves the
object through a distance.
(W = F x d)
Joule - unit of energy. (joule = newton-meter)
Power - rate of doing work or transferring
energy.
Watt – unit of power. (watt = joule/sec)
Energy - ability to do work.
Kinetic Energy – energy due to motion.
Potential Energy – stored energy, due to
position.
Machine – a device that helps work to be
done by multiplying input force at the
expense of distance.
Fulcrum – pivot point
Pulley – machine that changes the direction
of applied force (and often multiplies it too).
Law of Conservation of Energy
-energy can not be created or destroyed.
It can only change forms.
Work
Work done is defined to
as the product of the
applied force and the
distance through which
the object moves.
Work = force x distance
joule
newton
meter
Unit: joule = N - m
The force is parallel to the direction of motion.
Or
Distance moved in the direction of the force.
Work is done when an object
changes height.
Work is done on an object moved
horizontally if there is a force in
the direction of motion.
Work can be positive or negative.
If force and displacement are in the same
direction, the work done is positive.
If force and displacement are in opposite
directions, the work done is negative.
The work done on an
object equals the change
in energy of the object.
W = DE
Find the amount of work done by a
weightlifter in lifting a 100 kg barbell a
distance of 3 meters.
W= F x d
= 100 kg x 10 m/s2 x 3 m
= 3000 N-m
= 3000 J
A golf cart moves to the right. The driver applies
the brakes. And stops the cart in 5 m. A constant
braking force of 900 N is applied over this
distance. What is the direction of the braking
force? How much work is done on the cart by this
force?
The braking force acts to the left.
W=Fxd
= - 900N x 5m
= - 4500 N-m
= - 4500 J
In the absence of friction, all
work should be the same
regardless of path taken.