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Machines and Mechanical Systems

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How were the great pyramids built?

How can giant buildings be made from objects too heavy to carry?

Up until relatively recently, we could only go so high. After a certain point, it just wasn't feasible to keep building up. In the late 1800s, new technology redefined these limits. Suddenly, it was possible to live and work in colossal towers, hundreds of feet above the ground.

Thousands of workers toiled on the pyramids of ancient Egypt, the cathedrals of Europe and countless other towers, while striving to create something awe-inspiring.

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How were the great pyramids built?

How are giant skyscrapers built?

Historians think that the ancient Egyptians used ramps to push or pull the stones to the top. But whether they used one ramp straight up each side or they used a ramp parallel to each side is still being debated.

Overcoming the force of gravity, wind and getting materials to greater heights are just some of the obstacles in designing and building skyscrapers.These problems are solved using science and technology by developing mechanical systems that make building skyscrapers possible.

A Ramp

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What is a machine?It is a device with moving parts that work together

to accomplish a task.

The great pyramids and skyscrapers were built using machines and mechanical systems.

Ramps Pulley Systems

Ramps and Pulleys

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Wheel and AxleGears

Levers

Ramps

Block and Tackle

Review of Simple Machines

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1.

9. 8.

7.6.

5.4.

3.

2.

13.

12.

10.

14.

Classify each of these simple machines.

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Machines……make our lives easier.

Try cutting down a tree without a saw. A complex

machine like a chainsaw makes our lives even easier.

Try opening a can

without a can opener.

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Input - Input -

Output Output --

Is everything you do to make the machine work.

You push the pedals.

Is the result of your work.

You go fast.

There are two basic factors to keep in There are two basic factors to keep in mind when studying mechanical mind when studying mechanical

systems:systems:

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Input, Output, and Resistance

Input

Output

Resistance

effort

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Mechanical Advantage

Little effort

Big Results

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Fo

Fi

MA =Output force (N)

Input force (N)

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Input

Output

Input

Output

How can you make it easier to lift the rock?How can you make it easier to lift the rock?

Resistance Resistance

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Input

Output

Which lever would make it easier to lift the rock?Which lever would make it easier to lift the rock?

Mechanical Advantage

Results

1 m

0.5 m0.5 m / 1 m = 0.5

Distance

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Input

Output

Which lever would make it easier to lift the rock?Which lever would make it easier to lift the rock?

Resistance

0.1 m

1 m

Mechanical Advantage

1 m / 0.1 m = 10

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Input

Output

Input

Output

Which lever is more efficient?Which lever is more efficient?

Resistance Resistance

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Input Force

Output

Which lever is more efficient?Which lever is more efficient?

Efficiency 5 N5 N

10 N / 5 N = 210 N10 N

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Which lever is more efficient?Which lever is more efficient?

Input Force

10 N10 N

5 N5 N

Efficiency

5 N / 10 N = 0.5

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(RE) DESIGN(RE) DESIGN

PROTOTYPEPROTOTYPE

TESTTEST

EVALUATEEVALUATE

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Work FormulaWork Formula

FF x d d = WWWork

(joules)Force Force

(newtons)(newtons)DistanceDistance(meters)(meters)

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Calculating Work in Joules

1 m

eter

1 m

eter

50 N50 N x 1 m 1 m = = 50 joules50 joules

50 N50 N

Force (N)Force (N) x Distance (m) Distance (m) = = Work (joules)Work (joules)

50 N50 N

How many joules would be needed to lift a 50 newton50 newton rock 1 meter1 meter?

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An inclined plane is a slanted surface used to raise a load from a lower level to a higher level.

The 2 meter2 meter ramp reduces the force from 50 N to 25 N.

1 m

eter

1 m

eter 2 m

eters

25 25 newtonsnewtons(effort)(effort)

25 N25 N x 2 m 2 m = = 50 joules50 joules

You can reduce the effort force required to lift the 50 N50 N rockrock by using a 2 meter ramp. Since the distance the rock is moved is doubled, the

effort force is reduced by ½ to 25 newtons25 newtons.

Force (N)Force (N) x Distance (m) Distance (m) = Work (joules)= Work (joules)

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50 N50 N50 N50 N

This 2 m2 m ramp enables 50 N rockrock to be lifted

1 m1 m with a force of 25 N.25 N.

Which inclined plane would be best to lift a rock 1 meter in height?

1 m

eter

1 m

eter 2 m

eters5 meters

10 10 newtonsnewtons(effort)(effort)

25 25 newtonsnewtons(effort)(effort)

1 m

eter

1 m

eter

25 N25 N x 2 m2 m = 50 joules == 10 N10 N x 5 m5 m

This 5 m5 m ramp enables 50 N rockrock to be lifted

1 m1 m with a force of 10 N.10 N.

10 N10 N x 5 m5 m = 50 joules25 N25 N x 2 m 2 m = = 50 joules50 joules

Force (N)Force (N) x Distance (m) Distance (m) = = Work (joules)Work (joules)

System ASystem A

System BSystem B

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1 m

ete

r

1 m

ete

r

ForceForce X distancedistance ForceForce X distance distance=

F x d = WSystem ASystem A

System BSystem B

The The WORKWORK is is EQUALEQUAL in Both Systems. in Both Systems.

Machines and mechanical systems Machines and mechanical systems DO NOT DO NOT reduce the amount of workreduce the amount of work, they just , they just make make

work easierwork easier!!