Simple Machines
There are 6 basic types of simple machines.
1. The inclined plane2. The wedge3. The screw4. The lever5. The wheel and axle6. The pulley
Inclined Plane
Inclined plane is a flat, sloped surface.
1. It allows you to exert your input force over a longer distance.
2. Mechanical Advantage = Length of incline
Height of incline
Wedge
A wedge is a device that is thick at one end and tapers to a thin edge at the other end.
1. When you use a wedge, instead of moving an object along the inclined plane, you move the inclined plane itself.
2. Mechanical Advantage=Length of wedge
width of wedge
Screws
A screw can be thought of as an inclined plane wrapped around a cylinder.
1. The threads of a screw act like an inclined plane to increase the distance over which you exert the input force.
2. The closer together the threads of a screw are, the greater the mechanical advantage.
1. Think of the length around the threads as the length of the inclined plane.
Levers
A lever is a rigid bar that is free to pivot, or rotate, on a fixed point (fulcrum).1. Think about opening a paint can. Pg. 426.2. Mechanical Advantage = Distance from fulcrum to input force ÷ distance from fulcrum to output force.
Classes of Levers
1. First-Class Levers – always change the direction of the input force. Ex. Scissors, pliers, seesaws.
1. Second-Class Levers – increase force, but do not change direction of the input force. Ex. Doors, nutcrackers, bottle openers.
Third-Class Levers – increase distance, but do not change the direction of the input force. Ex. Fishing poles, shovels, baseball bats
Wheel and Axle
A wheel and axle is made of two circular or cylindrical objects fastened together that rotate about a common axis. The larger radius is the wheel The smaller radius is the axle Ex. Screwdriver, doorknob, steering wheel.
Pulley
A pulley is made of a grooved wheel with a rope or cable wrapped around it.
1. decreases the amount of input force needed and changes direction of input force. Ex. flagpoles
Types of Pulleys
1. Fixed Pulley – does not change amount of force. Only changes the direction of force.