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# Simple Machines - PowerPoint PPT Presentation

Simple Machines. The need to know. Inclined Plane. What is an inclined plane? A ramp that moves an object from a lower to a higher level. How does an inclined plane make work easier? By spreading the work over a longer distance How does an inclined plane give us a mechanical advantage?

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The need to know.

• What is an inclined plane?

• A ramp that moves an object from a lower to a higher level

• You do not need to know about the measurements and newtons.

• Inclined Plane Video

• Objective: To show how the steepness of an inclined plane can affect the amount of force necessary to do work.

• Procedure:

• 1. Make a stack of books about six inches high. Form two ramps of different lengths by leaning a ruler and a yardstick up against the top of the stack.

• 2. Loop a rubber band through the eye screw in the end of a wooden block. Place the block at the end of one ramp with the rubber band end toward the ramp.

• 3. Pull the block up one ramp. Try again using the other ramp.

• 4. Notice how much the rubber band stretches. How does the steepness of the ramp affect the rubber band? If you had to move a heavy piano into a moving van, would you rather have a short, steep ramp or a long, less steep ramp? The work to be done is the same in each case. Since work = force x distance, moving the piano into the van over a longer distance means less force is required.

• What is a wedge?

• A wedge is one or two inclined planes put together

• It may lift, pierce or cut an object. It can also fasten two objects together

Wedge Examples – What does each do? Pierce, cut, lift or fasten?

Pierce

Cut

Cut

Cut

Lift

Fasten

• Give each child a large slice of an apple.

• Have them take one bite using their incisors (front teeth). Have take a second bite using their back teeth (pre-molars or molars). Which was easier? Your sharp incisors are like wedges. They slice into and divide the apple slice. Your pre-molars are like those square blocks. As children finishing eating their apple slices

• Let them each have a turn cutting other apple slices with a kitchen knife/butter knife and a paring knife. Which is easier to use? The thinner the tip/sharper the blade of a wedge, the better it will be at exerting equal pressure in both directions and slicing through what you want to cut through. That's why it's best to sharpen knifes, plows, hoes, etc.

• What is a screw?

• An inclined plane wrapped around a core (spiral)

• Used to fasten objects or lift heavy objects

• How does a screw make work easier?

• By spreading the work out over a longer distance

• How does a screw give us a mechanical advantage?

• Allowing us to use less effort to fasten or raise objects

• Screw Experiments

• Wedge and Screw Video

• What is a lever?

• A bar that rests on and turns around a point

• Levers lift or move objects

• 3 parts (fulcrum=turning point, load=thing you want to move, effort=force you apply to a part of the lever)

• How does a lever make work easier?

• It puts some of the work on the fulcrum

• The closer the fulcrum is to the load the easier it is to lift or move the load

• How does a lever give us a mechanical advantage?

• Allows us to use less force and to change the direction of force

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Lever Experiment fulcrum?

• Try this experiment!

• Lever Experiment

Lever Video fulcrum?

• Lever Video

Wheel and Axle fulcrum?

• What is a wheel and axle?

• A simple machine that has a wheel that turns around a rod called an axle

• They help move, turn or lift objects

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Wheel and Axle Experiment fulcrum?

• MATERIALS:

• -2chairs, broom handle, string, bucket with handle, masking tape, scissors, ruler

• INSTRUCTIONS:

• 1. Place the chairs back to back, about 30 cm apart. Rest the broom handle across the back of the chairs.

• 2. Tie a 50 cm length of string to the bucket handle.

• 3. Tape the free end of the string to the middle of the broom handle.

• 4.Place a few marbles or some other light objects in the bucket.

• 5. Turn the broom handle with your hands to raise the bucket into the air. Turn it back the other way to return the bucket to the ground.

• 6. Tape the ruler straight up and down the broom handle near one end.

• 7. Use the ruler, which acts as a wheel, to turn the broom handle and lift the pail.

• QUESTIONS:

• 1. Could you lift the bucket by turning the broom handle with your hands?

• 2. Was it easier to lift the bucket when you turned the broom handle using the ruler?

• 3. Replace the ruler with a stick that is longer than the ruler and use the stick to turn the broom. Was it easier to lift the bucket using the long stick?

• 4. Identify the axle in the setup.

• 5. Identify the wheel in the setup.

Wheel and Axle Video fulcrum?

• Ignore the equations, it is more advanced.

• Wheel and Axle Video

The Pulley fulcrum?

• What is a pulley?

• A rope on a grooved wheel

• Help lift or move an object

• How does a pulley work? fulcrum?

• Spreads the work out over a longer distance

• How does a pulley give us a mechanical advantage?

• Allows to change the direction of the force

Pulley Examples fulcrum?

Pulley Experiment fulcrum?

• Watch this video and give it a try at home.

• Pulley Experiment

Pulley Video fulcrum?

• Pulley Video