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Do Now 10/29/14
5 minutes
•
Take out Scratch Paper and Calculator for our Jeopardy Review
– Write down formulas
– PE = mgh, KE = ½mv2, TME = PE + KE
Gravitational P.E= (1/2)kx2
• Position One winner person EARNS 3 points of extra
credit! Position Two earns 2 extra points, and third
winner will choose 1 extra point.
• Only one i-pad should be used in the group of four, with
scorer included.
Jeopardy Rules
• One common problem from the group will
be selected and anyone who gets it first
right, will score points and will choose the
next category.
• If a person answers incorrectly or can’t
explain the reasoning, next team person has
chance to steal, then next time. BE
PREPARED!
• First three Winning people will get extra
Work
PE
KE
Conservation of
Energy
100
100
100
100
200
200
200
200
300
300
300
300
400
400
400
400
500
500
500
500
Positive work if force is in the SAME direction as
displacement.
Negative work if force is in the OPPOSITE direction as
displacement
How do you determine when a force is
doing POSITIVE or NEGATIVE work?
Row 1, Col 1
height / increasing its height
Gravitational Potential Energy of an
object depends on its mass and
__________. You can increase an
object’s Potential Energy by
__________________.
Row1,Column2
the object is moving.
An object only has Kinetic Energy
if ______________________.
1,3
stays constant
According to the Law of Conservation
of Energy, the total amount of mechnical
energy ___________.
1,4
F1 is doing zero work because it is perpendicular to
motion.
The object below is moving to the left. Which Force is
doing zero work?
F1
F2
2,1
7350 J
A 75 kg man is on a ladder that
is 20 m tall. What is his
Potential Energy when he is
halfway up the ladder?
2,2
TRUE – KE doesn’t depend on direction.
Two cars of equal mass are traveling in
opposite directions at the same speed.
TRUE or FALSE – Both cars have
EXACTLY the same amount of Kinetic
Energy.
2,3
Remember that TME = PE + KE
A diver of mass 50 kg freely falls from a diving board
located 15 m from the water. Fill in the following table
• 2,4`` about the diver’s mechanical energy.
Height
PE
KE
TME
15 m
7350 J
0
7350 J
7350 J
7350 J
0
water) 0
0 (at
(at water)
W1 = 16000 J, W2 = -6000 J
If the object travels 20
m up, how much work
is done by F1 and F2?
F1 = 800 N
F2 = 300 N
3,1
PE = 40,000 J
Spiderman weighs
1000 N. He climbs
up the side of a
building. What is his
potential energy
after climbing 40 m?
3,2
4 kg bowling ball (32 J)
Which object has more
Kinetic Energy?
A 4 kg bowling ball
traveling at 4 m/s
Or
An 8 kg bowling ball
traveling at 2 m/s
3,3
PE = 3920 J, KE = 3920 J
A sled of mass 20 kg is at
rest at the top of a 40 m tall
hill. Ignoring friction, how
much Kinetic Energy and
Potential Energy does the
sled have when it is
halfway down the hill?
3,4
Work done on object is -5000 J
3 Forces are acting on an object. F1
500 N to the left. F2 400 N to the
right. F3 is 200 N to the right. If the
object has a displacement of 50 m to
the left, how much work was done on
the object?
4,1
∆PE = PEf – PEi = -9800 J
Tarzan climbs down a vine. If his mass is 200 kg, what
is his change in potential energy when he climbs from
15 m to 10 m off the ground?
4,2
KE = 159,438.78 J
A car of weight
5000 N is
traveling at -25
m/s. How much
Kinetic Energy
does the car have?
4,3
PE = 24.5 J, KE = 85.75 J
A coconut of mass 1.25 kg is
attached at the top of a tree of
height 9 m.
When the coconut falls off,
how much PE and KE will it
have once it falls to a height
of 2 m?
4,4
Work done on book is 117.6 J
A 3 kg Physics textbook falls
from a shelf that is 4 m from the
ground. Find the work done on
the textbook while falling from
the shelf to the ground.
5,1
Potential Energy is the maximum amount of work that
gravity can do to an object because work done by gravity
of an object that has fallen is found by multiplying Fg by
its height from the ground. Potential Energy is calculated
the same way.
Explain the relationship between
gravitational Potential Energy and
the work done by gravity on a
falling object.
5,2
KE = 480 J, v = 34.6 m/s
A baseball pitcher is throwing a
baseball of mass 0.8 kg.
After the pitcher applies a
force of 120 N over a
displacement of 4 m,
a)
How much KE does the
baseball have?
b) How fast is the baseball
traveling?
5,3
speed at bottom of loop = 22.18 m/s
A roller coaster cart is
traveling 10 m/s at the
top of a loop. If the loop
is 20 m tall and the cart
has a mass of 300 kg,
how fast is the cart
traveling at the bottom
of the loop?
5,4