Simple MachinesA machine is an invention that makes work easier.

Remember that Work = Force x DistanceA simple machine changes:

the strength of a push or a pull force or the distance of a movement, to complete a task more easily.

This produces a MECHANICAL ADVANTAGE

WEDGETwo inclined planes placed back to back

INCLINED PLANEAny slanting flat surface

PULLEYA circular lever that consists of a

grooved wheel rotating about a hub

SCREWAn inclined plane wrapped

around a cylinder

WHEEL & AXLEA fixed wheel turning on a rod through its center

LEVERA rigid bar that rotates on

a pivot called a fulcrum1st Class

Fulcrum in middle2nd Class

Load in middle3rd Class

Effort in middle

The Six Simple MachinesDID YOU KNOW?

All simple machines are derived from

either the inclined plane or the lever.

Inclined PlaneAn inclined plane or ramp is one of the simplest machines.

An inclined plane is a slanting surface connecting a lower level to a higher level.

It is easier to push something up a gentle ramp than up a steep one.

Does using an inclined plane decrease force or distance?

Force is decreased but distance is increased so work stays the same

The great blocks of stone that made the pyramids weren't lifted into

place they were rolled up ramps, or what we now call inclined planes.

The inclined plane, one of the simple machines, allows you to raise

great weights with small forces.

Perhaps rollers gave an inventor the idea for the wheel!

We’ll talk more about wheels later!

WedgeWedges are really a kind of inclined plane, but they

are so useful that people give them their own category. A wedge is two inclined planes aligned back to back which ends in a sharp edge and separates material.

How does a wedge increase force? Hint: Look at yellow diagram.

When the force is applied downward on a wedge, it is able to

push outward in two directions.

LeversA lever is a simple machine made with a rigid arm or a bar.

It has a fixed pivot or fulcrum where it turns. If you add a push or pull force (effort) on one end of a see-saw,

the other end goes in the opposite direction. The resisting weight is called the load.

A light person can balance a heavier person on a see-saw. The lighter person must sit further from the pivot.

What could this little bear change in order to lift the bigger bear?

If she moves the fulcrum closer to the load she will need less force to lift it.

Fulcrum in middle Load in middle Effort in middle

Three Classes of Levers

Wheel and AxleThe wheel and axle is generally considered to be a

circular lever, disk-shaped object with a hole in the center. This “wheel” is attached to a cylindrical rod called an axle. These two parts rotate

together so that force is transferred from one to the other. The wheels turn around the axle, which is attached to some type of vehicle.

The invention of the wheel is one of the most important in the history of man, similar in importance to the discovery of fire and the

development of writing, and electricity. What changes when the force transfers from axle to wheel?

Did You Know?Gears are wheels with teeth that

can be used to gain force or speed or change direction.

The wheel goes a further distance with the same forceWhat changes when the force transfers from wheel to axle?

The force applied to the axle is increased

PulleysA pulley is another special kind of wheel.

It has a groove on the outside for a string or rope. You can raise a flag up a pole with a simple pulley.

When you pull down on the rope, the pulley turns and the flag goes up.

Making work easierWith two pulleys you canlift twice as much weight

with the same effort. Withmore pulleys you can lift

even heavier loads.

How does a pulley produce a mechanical advantage?

Did You Know? A fixed pulley is fastened to one spot, and does not move around.

It provides no gain in force, distance or speed, but it changes

the direction of the force

By adding more ropes to share the load

ScrewsA screw is an inclined plane wrapped around a cylinder.

It holds things together or lifts materials. It has a groove called a thread which winds around a spiral shape.

When you turn a wood screw the thread cuts into the wood. With each turn the screw is pulled into the wood by one thickness of the thread.

You can’t push a screw into wood with your bare hands. The screw thread multiplies your strength by winding the screw in, a little at a time.

How a screw worksScrews multiply effort. Allthe effort to turn them isconcentrated into a smallmovement inwards. Thisproduces a very large force.

How is a screw like a wedge?It increases the force

1. This is an example of:a) Inclined Planeb) Pulleyc) Screwd) Lever

Checking Understanding

2. Which of the following statement is true?a) b is the fulcrum, c is the resistance, a is the effortb) b is the resistance, c is the fulcrum, a is the effortc)b is the fulcrum, a is the effort, c is the resistance.d) b is the resistance, a is the fulcrum, c is the effort

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3. A simple machine that is actually a kind of inclined plane is aa) pulleyb) wedgec) geard) balance

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4. Decreasing the slant of an inclined plane increases its.a) effort forceb) Mechanical Advantageb) Powerd) Work output

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5. A screw is an example of a (an) a) Inclined Planeb) Wedgec) rampd)pulley

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6. A pulley is an example of a (an) a) Inclined Planeb) Wheelc) rampd)pulley

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7. When you turn the screw it moves forward(a) with a smaller force(b) with the same force(c) by a greater distance(d) with a greater force

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EDHEADS SIMPLE MACHINES