ENERGY ≡ The ability to do WORK
An object that has
100 Joules
of
ENERGY
has the ABILITY to do
100 Joules
of
WORK
WORK ≡ Force · Distance
Power is how quickly work is done.
Power is how quickly energy is used.
POWER
≡
WORK
Time
Force·Distance
•
Explain how
WORK
and
ENERGY
relate
to
simple machines
such as
pulleys
,
levers
, and
inclined planes
.
•
Define :
Actual Mechanical Advantage
Theoretical Mechanical Advantage
Efficiency
IN
OUT
WORK
WORK
Machines
100% Efficient
“Ideally” or “Theoretically”
Distance
Force
Distance
Force
IN
OUT
Machines
100% Efficient
“Ideally”
Distance
Force
Distance
Force
IN
Mach
OUT
ine
Machines
Mach
ine
Machines
“Ideally”
100% Efficient
WORK
IN
= WORK
OUT
Force
IN
· Distance
IN
= Force
OUT
· Distance
OUT
Distance IN
Distance OUT
Force IN
Force OUT
http://www.acehardware.com/product/index.jsp?productId=1278574
http://image.truckinweb.com/f/opinions/standard-taxi-defines-extreme-form-follows-function/6294094+w600+cr1+re0+ar1/standard-taxi-wheelchair-ramp.jpg
1.6 m
0.4 m
150 lbs
Work
in
= Work
out
f
in
∙ d
in
= f
out
∙ d
out
f
in
∙ 1.6
= 150∙ .4
f
in
= 37.5 lb
? F
Force IN
Force OUT
x
Mechanical
Advantage
=
What is the ADVANTAGE to using machines?
Force
INForce
OUT
Actual
Mechanical Advantage
=
Some
Number
Distance
IN
Force
IN
Distance
OUT
Force
OUT
Distance
IN
Force
IN
Distance
OUT
Force
OUT
Mechanical
Advantage
=
What is the ADVANTAGE to using machines?
Some
Number
Distance IN
Distance OUT
Theoretical
Mechanical Advantage
=
Distance OUT
Distance IN
IN
OUT
WORK
WORK
IDEALLY
WORK
WORK
IN
OUT
100 Joules
100 Joules
IDEALLY
In Reality
100 Joules
76 Joules
IN
Efficiency
OUT
WORK
WORK
Efficiency =
IN
Efficiency
OUT
Efficiency =
Distance
Force
Distance
Force
Efficiency =
Force
OUT
Force
IN
Actual
Mechanical Advantage
=
Theoretical
Mechanical Advantage
=
Distance
IN
Distance
OUT
Efficiency =
Work
OUT
Actual
Mechanical Advantage
Force
OUT
Force
IN
Theoretical
Mechanical Advantage
Distance
IN
Distance
OUT
Efficiency
Work
OUT
Work
IN
Ideally! (50 N)(3 m) = (150 N)(1 m)
In Reality! (50 N)(3 m) = (140 N)(1 m)
150 Joules = 150 Joules
150 Joules = 140 Joules
= 2.8
140 N
50 N
= 3
3 m
1 m
= 93 %
140 J
150 J
=
2.8
3
IN OUT
100
lbs
100
lbs
100
lbs
100
lbs
100
lbs
100
lbs
100
lbs
100
lbs
100
lbs
300
lbs
100
lbs
100
lbs
300
lbs
300
lbs
900
lbs
300
lbs
100
lbs
A pulley
only
changes the
direction
of
the force!
It does not
Class III
Class I
Class II
LEVERS
Angle-Angle Similarity Theorem
If two angles of one triangle are congruent to two
angles of another triangle, then the two triangles are
similar, and corresponding sides are in proportion.
Fulcrum “pivot”
d
IN
d
OUT
d
Load
d
Effo
rt
MA = =
d
in
d
out
d
Effort
http://
hometown.aol.com/sdmcgil/images/natural%20wheelbarrow%20on%20drive.jpgForce
IN
· Distance
IN
= Force
OUT
· Distance
OUT
Mechanical Advantage = 3
MA = =
d
in
d
out
d
Effort
Force
IN
· Distance
IN
= Force
OUT
· Distance
OUT
Mechanical Advantage = 1
Mechanical Advantage = 3
MA = =
d
in
d
out
d
Effort
http://www.homedepot.ca/wcsstore/HomeDepotCanada/images/catalog/14-569_mid_res_4.jpg
Force
IN
· Distance
IN
= Force
OUT
· Distance
OUT
Mechanical Advantage = 6
http://www.northwaysmachinery.com/images/products/detailview/MIDWEST%20P167BW.jpg
MA = =
d
in
d
out
d
Effort
http://images.google.com/imgres?imgurl=http://www.consumershero.com/image_wp/funny_cars_pictures/crash_boat_jeep.jpg&imgrefurl=http://www.consumershero.com/archives/category/funny-accidents/&usg=__KF6TGhB38o-a4BF9ipBQ1wjZUN4=&h=448&w=494&sz=76&hl=en&start=30&tbnid=esS1A2EwtCgb3M:&tbnh=118&tbnw=130&prev=/images%3Fq%3Dstuck%2Bjeep%26start%3D20%26gbv%3D2%26ndsp%3D20%26hl%3Den%26sa%3DN
MA = =
d
Effort
d
Load
d
in
http://pergatory.mit.edu/perg/PERG_Pictures/Snowbird_2001/Touring_Salt_Lake/backhoe.JPG
Force
IN
· Distance
IN
= Force
OUT
· Distance
OUT
Mechanical Advantage = ¼
MA = =
d
in
d
out
d
Effort
http://www.alyon.org/InfosTechniques/biomedical/medical/le_corps_humain/images/le_biceps.gif
WORK
IN
= WORK
OUT
Force
IN
· Distance
IN
= Force
OUT
· Distance
OUT
Mechanical Advantage = 1/9
http://anybody.auc.dk/repository/images/
