Wheel and Axle, a Simple Machine
Purpose: Understanding the wheel and axle concept and what a great advantage a screwdriver handle gives you because it is a “Simple Machine.”
Overview: Simple Machines is a teem used in physics to make it easier to do work. Leavers, inclined planes, pulleys, wedges, screws, and wheel-and-axles are examples of simple machines. With the simple machine called a wheel and axle, movement over a bigger distance gives a stronger force over a smaller distance.
Imagine trying to open a door if the knob is missing and only the small shift is there! The doorknob is like a big wheel; the knob covers a bigger distance when it is turned but makes it easy to turn the shaft. Think about steering a car without the steering wheel or closing a submarine’s watertight hatch without the wheel on the door.
A wheel and axle tool may not actually have a wheel but simply a “spoke” that is rotated in a circular direction, like a wheel. An example of this type of wheel and axle is a pencil sharpener. When you turn the handle, you are covering a larger distance than the turning sharpening blades inside, but a greater force is gained at the blades. Using a socket wrench is another example , where you turn over a small distance, and the other end of the bat moves over a greater distance, but with greater force.
Sometimes the opposite is needed- a little distance and a lot of force yields a smaller force but a greater distance. An example of this is swinging baseball bat. At the handle, you put a lot of force into the bat and turn over a small distance, and the other end of the bat moves over a greater distance, giving it more speed.
Show the concept of wheel and axle using a screwdriver and a few friends. A screwdriver is a simple machine-a wheel and axle. Turning the bigger handle gives a bigger force at the smaller blade end.
Hypothesis: No matter how much I try, I will not the able to a turn a screwdriver by the blade using only my hand while a friend holds the handle.
- screwdriver with a large handle
- pair of pliers
- a friend
Procedure: Have a friend hold the handle of a fairy large screwdriver. Tell your friend to try to keep it from turning. Grab the blade with one and and try to turn the screwdriver while your friend holds the handle. Even if your friend is weaker than you, you will not be able to turn the screwdriver. Try to grasp and turn the shaft using two hands instead of one. Are you able to turn it at all?
Using a pair of pliers, bow try to turn the blade (hold the pliers perpendicular to the screwdriver shaft). Is your friend still able to hold the handle and keep it from turning? What if your friend uses two hands?
The pliers are a wheel and an axle too, and the pliers form a much bigger spoke of the wheel than the screwdriver handle. The longer the length of the turning spoke, the more force you get from it, but the more distance must be traveled.
Results and Conclusion: Write down the results of your experiment. Come to a conclusion as to whether or not your hypothesis was correct.
Something more: Try to turn a long thin screw into a piece of wood with your bare hands by turning the shaft. Is it impossible? Then try a screwdriver. Is it easy to do, or easier? If the wood is very hard, try using the pliers to help turn the shaft whole you press down on the screwdriver. What happens now?