Chapter 4.3a M Types of Machines

All machines are made from 6 simple machines – lever, inclined plane, wedge, screw, wheel and axle, and pulley. Examples are screwdrivers as a lever, ramp is an inclined plane. We are going to look at each simple machine.

Levers A lever is a simple machine made of a bar that pivots at a fixed point, called a fulcrum. Levers apply a force to a load. There are 3 types of levers classified by the location of the fulcrum, the load, and the input force.

First Class Lever In a first class lever the fulcrum is between the input force and the load. They work by changing the direction of the input force. They can be used to increase force or increase distance. Examples: Using a hammer to remove a nail, a seesaw (teeter totter), rowing a boat.

Second Class Lever In a second class lever the load is between the fulcrum and the input force. Second class levers do not change the direction of the input force, but allow less force. The output force will be greater than the input force so you have to exert the force over a larger distance. Examples: a wheel barrow and a bottle opener.

Third Class Lever The input force is between the fulcrum and the load. Third class levers do not change the direct of the force so they do not increase the force. The output force is less than the input force. Examples: A hammer and your arm.

Inclined Plane An inclined plane is a straight, slanted surface. A ramp is a good example. Inclined planes make work easier. Loading something in the back of a truck is easier using an inclined plane than just lifting the object. Mechanical advantage of inclined planes – the longer the inclined plane is compared to the height the great the mechanical advantage. To find the mechanical advantage of an inclined plane divide the length of the inclined plant by the height the load is lifted.

Wedges A wedge is a double inclined plane that moves. It applies a force on an object. The output force is greater than the input force, so the input force must be applied over a greater distance. Examples of wedges: a knife, doorstop, plow, axe heads, and chisels. Mechanical advantage of wedges: The longer and thinner the wedge the greater the mechanical advantage. To find the mechanical advantage you divide the length of the wedge by its greatest thickness.

Screws A screw is an inclined plane wrapped in a spiral. The screw applies a large force through the short distance. You apply a small input force and get a large output force. Mechanical advantage of screws: The longer the spiral on a screw is and the closer together the threads the greater the mechanical advantage.