Force and Motion: How do simple machines help us move objects?

Force is a push or a pull, and is measured in Newtons, which is a unit of force. Motion is a movement.


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Lift (Pull Up)

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Using a push-pull meter, we prove that it takes more force to lift (pull up) than the push or pull sideways.

In science, work is accomplished when you put force into an object and the object moves. If the object does not move, no work was accomplished. Simple machines help us accomplish work using less force (effort). Although simple machines help us use less force, we need to move objects further. For example, although it is easier to drag something up an inclined plane (ramp) than lifting it, it is further to go up the ramp.

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In a lever, the closer the fulcrum is to the load, the less force it takes to lift the load. However, there is a tradeoff. When the fulcrum is close to the load, you cannot lift the load very far. When the fulcrum is far from the load, it takes more force to lift the load, but it also goes further up.

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Whenever two things rub together, friction happens. "Friction is a force that slows moving things down and turns the moving energy into heat energy." Whenever you rub your hands together, you can feel the heat of friction. All objects, no matter how smooth, have tiny bumps and pits that causes objects to slow down as they slide past each other. Without friction, we would not be able to walk. For example, ice is slippery to walk on because it it is smoother and has less friction than pavement, which is rougher.

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When there is too much friction, it can be difficult to do things. For example, taking off a ring is tough when your hand is dry and the ring is small. If you use soap or oil, then your ring slips off easily. Lubricants (like soap or oil) are slippery substances (things) that make objects smoother. Lubricants reduce the amount of force needed to move an object.

Wheels also reduce the amount of force needed to move an object. The ancient Egyptians were able to use wheels or dowels to move enormously heavy stones to build the pyramids.

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A second type of simple machine is a wheel and axle. Examples include: doorknobs, screwdrivers, steering wheels, and rolling pins. They move in the same direction (look at arrows in the picture below). It is easier to move a weight with a wheel and axle than with our bare hands.

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Gears are a third kind of simple machine. A gear is a wheel with teeth. The smaller the gear, the faster it moves. A gear will make the gear next to it move in the opposite direction. There are gears inside clocks, bicycles, cars, and other machines.

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Gears inside a clock

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Example of a pulley in a construction site

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1. Video: Bill Nye on Simple Machines (Part 1)

2. Video: Bill Nye on Simple Machines (Part 2)

3. Video: Bill Nye on Simple Machines (Part 3)

4. Force and Motion Unit Summary

5. Force and Motion worksheets

6. Bill Nye on Friction

7. Website further explaining simple machines

8. Roller-coaster physics video