Wheel and Axle Lever Simple Machines Pulley Screw Wedge Inclined Plane

What is a simple machine? A simple machine is a machine that has few or no moving parts. Lever Inclined Plane Screw Wedge Wheel and axle Pulley

Why are they Useful? Simple machines are useful because they can make a physical job easier by changing the magnitude or the direction of the force exerted to do work.

What is work? Work is defined as a force acting on an object to move it across a distance. Furniture movers do work when they move boxes. Gardeners do work when they pull weeds. Children do work when they go up and down on a seesaw.

How did their work get easier? Movers use a ramp and dolly to move boxes. Gardeners use a shovel to help break through weeds. Children use the seesaw as a lever to move up and down.

Example Have you ever tried to unscrew a nut, bolt, or screw from something with your bare hands and discovered that it was just too tight to loosen even if you had a good grip?

The wrench and screw driver are examples of a wheel and axle, where the screw or bolt is the axle and the handle is the wheel. The tool makes the job easier by changing the amount of the force you exert. Wheel Axle

Levers Lever Load Fulcrum

Function A lever is a long rigid bar that sits on and pivots around a fulcrum. A lever allows for an effort force to be applied to one side of the bar and it causes the load at another place on the bar to move.

Inclined Plane

Function An inclined plane is a flat surface that is higher on one end. An inclined plane is a simple machine which allows us to raise an object with less effort than if we lifted it directly upward. The trade off to pulling up a ramp instead of just lifting it, is that you travel a longer distance.

Screw

Function A screw is an inclined plane wrapped around a shaft or cylinder. Screws hold things together. It takes less force to screw a nail than it does to pound a nail-but you have to twist many times to get the screw in.

Wedge Two inclined planes make a wedge.

Function A wedge is two inclined planes joined back to back. The wedge is a simple machine that allows us to apply a force down onto the wedge and the force is redirected to the sides to split things.

Wheel and Axle Wheel Axle

Function Wheel and Axle The axle is a rod that goes through the wheel which allows the wheel to turn.

Pulleys Wheel Rope This box is easier to lift because of the pulley.

Function A pulley needs a rope, chain or belt around the groove to make it do work A pulley is a simple machine that can be used to change the direction of an applied force and when used in certain combinations can let us apply less force to accomplish work.

Diagrams of Pulleys Fixed pulley: A fixed pulley changes the direction of a force; however, it does not create a mechanical advantage. Movable Pulley: The mechanical advantage of a moveable pulley is equal to the number of ropes that support the moveable pulley.

COMBINED PULLEY The effort needed to lift the load is less than half the weight of the load. The main disadvantage is it travels a very long distance. 

Mechanical Advantage and Efficiency Mechanical Advantage is how much easier and faster a machine makes your work is the mechanical advantage of that machine. In science terms, the mechanical advantage is the number of times a machine multiplies your effort force. Mechanical efficiency measures the effectiveness of a machine in transforming the energy and power that is input to the device into an output force and movement.

Compound Machines Simple machines can be put together in different ways to make complex machinery.