# Simple Machines

Today we’re going to briefly go over one simple machine, the wheel and the axle. The wheel and the axle categorized as a simple machine and we want to talk about mechanical advantage of the wheel and axle.

Essentially with the wheel and an axle, most people tend to think about automobile tire, because that’s usually what we talk about, is a wheel and an axle.

Mini-test: SIMPLE MACHINES

Question 1: A knife is an example of which simple machine(s)
A.
B.
C.
D.
Question 2: Which of the following is NOT an example of a wheel and axle?
A.
B.
C.
D.

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Two wheels attached by an axle, but what we want to think about to help illustrate the point of the mechanical advantage of the wheel and axle is something more along the lines of the steering wheel.

Essentially, the steering is done by the central column, but if you had to grip that central column and turn it with your hand this way it would be almost impossible. By attaching a wheel to that central axle and moving the radius of that circle out, it takes much less force to turn the central axle and knowing therefore to turn the car. What you have then, is a mixture of one type of force, the wheel attached to the axle making it easier then, to do what you would ordinarily have to exert a great deal of force, if you grab the main axle itself and tried to turn it by itself.

I’ve got a picture here, this is the central axle here, this is the outer wheel of the steering wheel. If we had to grab the central column and turn it, it would be almost impossible for us to get enough force. But you move the wheel out, attach the axle and you apply force out here and it becomes much easier to turn here. Force here translates here to greater force, so the mechanical advantage increases with the radius.

I’ve got an example up here, we’ve got a radius of 12 versus a radius of 10, with our axle over here, the mechanical advantage increases with the radius. Bigger radius 12 means greater mechanical advantage. What we mean by that is if the same amount of force was applied to the outer wheel at 10 inches and the same amount of force applied to the wheel at 12 inches, you would get a much greater advantage at the 12 inch radius than at the 10, assuming the same amount of force is applied.

It translates here to the central axle much greater, so mechanical advantage is greater, the larger the wheel is and in the same way we’ve got a larger wheel, it takes less force to turn it. If you think about it, sometimes in little sporty cars, they have sort of smaller steering wheels, but when you get to something as big as a bus or an 18 wheeler, they usually have very large steering wheels. And this is just an application of the simple machine, the wheel and the axle, the mechanical advantage increasing as the radius also increases. Well, this has been a basic overview then of the simple machine, wheel and axle.

Next Lesson: Sound