In terms of motion, what does

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In terms of motion, what does energy allow you
to do?
WORK

Units?
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How much work is done in each?
A man squats 200 kg masses a distance of 0.5 m.
A waiter carries a 10 kg tray 10 m across the
room.
A 65 kg woman skies down from the top of
Schweitzer (el. 1951m) to the lodge (el. 1220m).
A child pulls on a rope with 10 N, dragging a
block 10 m across the floor which the rope makes
a 30o angle to.
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WORK Force Distance
Force and Distance have to be in the SAME
DIRECTION
How much WORK is done by the fork lift?
ZERO!
W f d
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WORK Force Distance
Force and Distance have to be in the SAME
DIRECTION
How much WORK is done by the fork lift?
Work force distance
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How much WORK was done in lifting the crate?
Work F d
http//www.aviationpics.de/prev/crane203.jpg
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How much WORK does the runner do?
600 N
5 m
3 m
Work F d
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How much WORK do these fitness buffs do as they
enter the gym?
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In order to do Work what must be expended?
ENERGY!
Work expended Energy required/given
What kinds of energy are there?
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Who did more WORK?
Which required more energy?
How can they be equal?... Isnt something
different?
Time is different so
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UNITS
WORKTime
POWER
Watts
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A 40 Watt light bulb Means
40 Joules of WORK done every second.
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The energy in a BIG MAC could run the 40 W bulb
for
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An average horse can lift 550 pounds a distance
of 1 foot in 1 second.
And do it all day long.
1 Horsepower 550 ftlbs/s
James Watt
550 lbs.
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How much time will it take the 2000 lb car to
climb the 80 ft hill if the engine is 115 Hp?
80 ft
Time 2.53 s
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FIELD TRIP
Calculate YOURHorse Power
Clifton Bluhm
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ENERGY The ability to do . . .
WORK
An object that has100 Joules of ENERGYhas the
ABILITY to do100 Joules of WORK Energy is
conserved!
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POWER is how quickly WORK is done.
POWER is how quickly ENERGY is expended.
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The Work Energy connection (in motion)
10,000 N of force applied for 10 m how much
work?
How much energy does the bus now have?
Wdone ?E
Energy appears to be based on velocity
Lets substitute in velocity somehow
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KE ½mv2

• A 1000 kg car is traveling at 25 m/s how much
  work must be done to stop it?
• If the Ff has a max value of 10,000 N what is
  the shortest distance that car can stop in?

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The Work Energy connection (potential)
The box has potential the potential to become
KE. How calculate its Potential???
40 m
How much KE at the bottom??? what is v???
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PEg mgh

• A 50 kg object hits the ground at 30 m/s how
  high was it dropped from?

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KE ½ mv2 WORK F d
1000 kg car
Assume the friction force is 10,000 N.
http//www.wolflink.net/jstorey/porsche/968/js968
aa.jpg
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KE PE applied But officer I was only going
10 over?