WORK

1
WORK
2
WORK
-Energy is used to affect matter -The two main
types of energy are ______________ (stored
energy) ______________ (energy of
motion)
potential
kinetic
-Work is the process of changing the ___________
or _____________ of an object.
kinetic e.
potential e.
-Throwing a football changes its speed, which is
a change in its _____________ energy. You
have done ________ to accomplish this.
kinetic
work
-Lifting an object off the ground changes its
position, which is a change in its
__________________ energy. You have done
__________ to accomplish this.
potential
work
3
-The work done when moving an object depends on
the size of the _____________ used and the
________________ the object moves. work
______________ x ________________
or
force
distance
force
distance
W
W F x d
F
d
x
-Since doing work changes an objects energy,
both work and energy are measured with the same
SI unit ______________ -Exerting a force of
one newton to move an object one meter _______
joule
1 joule (J)
J N x m
4
Ex. Spiderman uses a force of 40 newtons to throw
a web-ball a distance of 12 meters. How much
work in joules did Spiderman do? Ex. The
She-Hulk does about 5000 joules of work to lift a
car above her head. If she lifts the car
approximately 2 meters, what was the force
required to lift the car?
F x d
W
W
40 N
12 m
x
480 J
W
W
F
2500 N
F
d
5000 J
5000 N x m
F

2 m
2 m
5
-If you recall, a machine is a mechanical device
that helps you do work. -Machines can do this by
allowing you to apply a __________ force over
a ____________ distance.
small
large
-To lift a car about 0.2 meters requires about
500 J of energy. (this is constant no matter
how you lift it, by hand or by machine) -Lifting
this car 0.2 meters straight up by hand would
require a force of _________ N.
2500
(562 lbs!)
500 J (or N x m)
W
F

F
0.2 m
d
-However, if we used a simple machine and applied
our force over a distance of 5 meter (instead
of the straight 0.2m), our force applied would be
__________ N.
100
(23 lbs!)
W
500 J (or N x m)
F

F
5 m
d
6
Review The six different simple machines
are _______________ _______________ ____________
__ _______________ _______________ ______________

inclined plane
screw
wheel axle
wedge
lever
pulley
-Some machines can make a job easier than others
can. -The force a machine applies to an object
compared to the force you apply to the machine
is called _______________ ________________.
_______________ or M.A. ----------
mechanical
advantage
actual mechanical advantage
F
Load/Output Force
LOAD
F
Effort/Input Force
EFFORT
-Mechanical advantage is the ratio of load force
to the effort force.
7
Ex. The super hero Daredevil uses his billy club
as a first class lever to pry open a door for his
escape. If Daredevil applies a force of 100 N to
the billy club and the club applies a force of
500 N to the door, what was the mechanical
advantage of using it?
F
500 N
LOAD
M.A.
5
M.A.

F
EFFORT
100 N
-Mechanical advantage can also be calculated from
the distance the machine parts move. The
ratio of effort distance to load distance is the
same as the ratio of load force to effort force.
Therefore M.A. ------------ Ex. If the
Daredevils billy club handle was pushed a
distance of 22 cm and the door opened a distance
of 4 cm, what was the mechanical advantage of
using the club?
d
EFFORT
(IDEAL)
d
LOAD
(This is higher because it doesn't include
friction)
d
22 cm
EFFORT
M.A.
5.5
M.A.

d
4 cm
LOAD