6 Types of Simple Machines

1. Inclined Plane

2. Wedge

3. Screw

4. Lever

5. Wheel & Axle

6. Pulley

Inclined plane – flat, slanted surface.

When an object is moved up an inclined plane, less effort is needed than if you were to lift it straight up, but, you must move the object over a greater distance.

Examples of Inclined Planes

Ideal Mechanical Advantage

Ideal Mechanical Advantage = length of incline

height of incline

What is the Ideal Mechanical Advantage?

6 meters

2 meters

Wedge- Device that is thick at one end and tapers at the other. Most wedges (but not all) are combinations of two inclined planes.

A knife, axe, razor blade, and teeth are all good examples of wedges. Generally it can be anything that splits, cuts, or divides another object including air and water.

In each example identify what is being split or wedged apart by each wedge in the above pictures.

– a rocket....

– a fan...

– a boat...

– teeth...

Air

Air

Water

Food

Screws

Screw- an inclined plane wrapped around a cylinder.

-changes the distance that you apply a force over

-the closer the threads are together, the greater the Mechanical Advantage.

Levers

1. Lever- rigid bar that is free to rotate (pivot) about a fixed point.

2. Examples- crow bar, door (hinge), sea-saw

3. Fulcrum- the fixed point that a lever pivots around.

4. Three Classes of LeversOpen Textbook to p. 391

a) 1st Class Lever: fulcrum in center positiona) Example: Sea-saw, scissors

a) 2nd Class Lever: output force in center positiona) Example: Door

a) 3rd Class Lever: Input force in center position.a) Baseball bat, rake

Lever Activity: • Objective- to compare the three types (classes) of

levers. Open textbook to p. 391.

• Create a First Class Lever– Place your index finger on the desk and balance the spoon on it.– Place bean in spoon bowl to represent output force.

• Create a Second Class Lever– Place the spoon bowl on the table and one finger at end towards

handle. – Where would bean go to represent output force?

• Create a Third Class Lever– Where would your finger and bean go?

Mechanical Advantage of a Lever

MA = Distance from fulcrum to input force Distance from fulcrum to output force

Wheel & Axel

Wheel and Axel

• Simple machine made of circular or cylindrical objects, fastened together and rotate together.

• The object(s) with the larger circumference (size) is the wheel.

• The object with the smaller circumference (size) is the axel.

Wheel Axel

• Distance of force is increased.

• Mechanical advantage is usually greater than 1.

Mechanical Advantage of a Wheel

MA = Radius of Wheel Radius of Axel

Gears

• Wheel with interlocking teeth.

• Form a compound machine when more than one gear is used.

Pulley

• A grooved wheel with a rope, cable, or chain wrapped around it.

• Direction of input force is changed.

Types of Pulleys• Fixed Pulley- attached to a structure

– Ideal Mechanical Advantage = 1

• Movable Pulley- attached to the object you want moved– Ideal Mechanical Advantage = 2

• Pulley System- combination of fixed and movable pulleys– Ideal Mechanical Advantage = 2 or more

– The ideal MA of a pulley system is equal to the number of sections of the rope that support the object.

Pulley Systems

Raising a Dumpsterhttp://www.youtube.com/watch?v=eaiyeQ8pJAA

Compound Machine

• A machine that utilizes two or more simple machines.

• Example: – Wheelbarrow has a wheel and axel & lever

What are examples of Compound Machines?

Car• Wheel & Axel• Gears• Levers

Can Opener• Gears (wheel &

axel)

• lever

Screws

Screw- ________________________________________________________________________________.

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