January 29, 2008
DRILL
Get out last night’s homework assignment
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TODAY’S OBJECTIVES
1. To review last night’s homework
2. To review 3D Quiz 2
3. To begin the Mechanical Basketball Player project
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HOMEWORK REVIEW
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• Machines are…
– artifacts that transmit or change the application of power,
force, or motion.
• What is an artifact?
– something created by humans usually for a practical
purpose.
• Machines can be simple or complex
– Complex machines are comprised of…. Simple Machines
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Principle: a law of nature underlying the
working of an artificial device
• Simple machines work on 2 basic principles:
LEVER
INCLINED PLANE
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• There are 3 classes of lever:
Third Class
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1.
A 1st-class lever is used to lift a bureau that weighs 80 lbs. The bureau
is located 3 feet from the fulcrum. A child who applies the force to the
other side of the lever has only 20 lbs. of strength to push. How far from
the fulcrum should the child apply the force? (HINT: Sketch a picture,
list the given information, write your equation, and solve for the
unknown)
L = 80 lbs.
3 ft.
DL = 3 ft.
DF = ?
F = 20 lbs.
DF = ?
F = 20
80 lbs.
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3 ft.
DF = ?
L = 80 lbs.
DL = 3 ft.
DF = ?
F = 20
80 lbs.
F = 20 lbs.
L x DL = F x DF
80 lbs x 3 ft = 20 lbs x DF
240 ft-lbs = 20 lbs x DF
20 ft
20 ft
DF = 12 ft
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3 ft.
DF = ?
L = 80 lbs.
DL = 3 ft.
DF == 12
DF
? ft
80 lbs.
F = 20
F = 20 lbs.
What is the Mechanical Advantage of
12 ft.
DFthis lever?
M.A.=
DL
=
3 ft.
= 4
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3 ft.
DF = ?
L = 80 lbs.
DL = 3 ft.
DF == 12
DF
? ft
80 lbs.
F = 20 lbs.
F = 20 lbs.
MA = 4
What does
F x MA = ?L
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2.
A gardener is capable of applying 40 lbs. to lift a wheelbarrow.
Her hands are placed 3 feet from the axle of the wheelbarrow.
The weight of the compost that she carries is 2 feet from the axle
of the wheelbarrow. What is the maximum weight of compost
she can carry?
L= ?
DL = 2 ft.
F = 40 lbs.
DF = 3 ft.
L x DL = F x DF
L x 2 ft = 40 lbs x 3 ft
L x 2 ft = 120 ft-lbs
2 ft
2 ft
L = 60 lbs.
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3 ft.
DF = ?
L = 60 lbs.
DL = 2 ft.
DF = 4 ft.
80 lbs.
F = 30 lbs.
F = 20 lbs.
What is the Mechanical Advantage of
4 ft.
DFthis lever?
M.A.=
DL
=
2 ft.
= 2
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3.
A water pump at the State Park is set up as a 3rd-class lever. The load that the
suction inside the pump weighs is 20 lbs. The distance from the load to the fulcrum
is 20 inches. The park ranger is wondering where an adult who can apply a force of
25 lbs. should put her hand to lift the pump. The ranger is also wondering where
another adult who can apply a force of 10 lbs. should put her hand to lift the pump.
DL = 20”
L = 20 lbs.
DF = 8”
problem is asking 2 questions. What are they?
DLThis
= 20”
F1 = 25 lbs.
DF = ?
L x DL = F x DF
20 lbs x 20” = 25 lbs x DF
400 in-lbs = 25 lbs x DF
25 lbs
DF = 8”
25 lbs
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3.
A water pump at the State Park is set up as a 3rd-class lever. The load that the
suction inside the pump weighs is 20 lbs. The distance from the load to the fulcrum
is 20 inches. The park ranger is wondering where an adult who can apply a force of
25 lbs. should put her hand to lift the pump. The ranger is also wondering where
another adult who can apply a force of 10 lbs. should put her hand to lift the pump.
DL = 20”
L = 20 lbs.
DF = 40”
DL = 20”
F1 = 10 lbs.
DF = ?
L x DL = F x DF
20 lbs x 20” = 10 lbs x DF
400 in-lbs = 10 lbs x DF
10 lbs
10 lbs
DF = 40”
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Get with a partner
Complete steps on notebook paper
KEEP IT NEAT!
Follow the rubric
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Ballistic Ideas
Ballistic Ideas
Initial Velocity (vi)
Range (x)
Firing Angle (theta)
Sketch of the Ballistic Device Setup
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Ballistic Ideas
Ballistic Ideas
Ballistic Ideas
Ballistic Ideas
Ballistic Ideas
Ballistic Ideas
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Ballistic Ideas