Get out last night’s homework assignment

January 29, 2008

DRILL

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1. To review last night’s homework2. To review 3D Quiz 23. To begin the Mechanical Basketball Player project

TODAY’S OBJECTIVES

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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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• Simple machines work on 2 basic principles:

LEVER

INCLINED PLANE

Principle: a law of nature underlying the working of an artificial device

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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)

80 lbs.

3 ft. DF = ?

F = 20 lbs.

L = 80 lbs.

DF = ?DL = 3 ft.

F = 20

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80 lbs.

3 ft. DF = ?

F = 20 lbs.

L = 80 lbs.

DF = ?DL = 3 ft.

F = 20 L x DL = F x DF80 lbs x 3 ft = 20 lbs x DF 240 ft-lbs = 20 lbs x DF 20 ft 20 ft

DF = 12 ft U3d-L9

80 lbs.

3 ft. DF = ?

F = 20 lbs.

L = 80 lbs.

DF = ?DL = 3 ft.

F = 20DF = 12 ft

What is the Mechanical Advantage of this lever?DF

DLM.A.= 12 ft.

3 ft.= 4=

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80 lbs.

3 ft. DF = ?

F = 20 lbs.

L = 80 lbs.

DF = ?DL = 3 ft.

F = 20 lbs.DF = 12 ft

MA = 4 What does F x MA = ?L

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2 ft 2 ft

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 = F = DF =

?2 ft.

40 lbs.3 ft.

L x DL = F x DFL x 2 ft = 40 lbs x 3 ft

L x 2 ft = 120 ft-lbs

L = 60 lbs. U3d-

L9

80 lbs.

3 ft. DF = ?

F = 20 lbs.

L = 60 lbs.

DF = 4 ft.DL = 2 ft.

F = 30 lbs.

What is the Mechanical Advantage of this lever?DF

DLM.A.= 4 ft.

2 ft.= 2=

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This problem is asking 2 questions. What are they?

L = DL = F1 = DF =

20 lbs.20”

25 lbs.?

25 lbs 25 lbs

L x DL = F x DF20 lbs x 20” = 25 lbs x DF

400 in-lbs = 25 lbs x DF

DF = 8”

DL = 20”DF = 8”

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.

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L = DL = F1 = DF =

20 lbs.20”

10 lbs.?

10 lbs 10 lbs

L x DL = F x DF20 lbs x 20” = 10 lbs x DF

400 in-lbs = 10 lbs x DF

DF = 40”

DL = 20”DF = 40”

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.

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Get with a partner

Complete steps on notebook paper

KEEP IT NEAT!

Follow the rubricU3d-L9

Ballistic Ideas

Range (x)

Firing Angle (theta)

Sketch of the Ballistic Device Setup

Initial Velocity (vi)

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