# Wheel+axle combination

1. Apr 7, 2015

### LogU16

Hello, Respected teachers.

Why wheel+axle combination is used? Why can we not only use the wheel?

And one more question; please give me an example of daily life in which we apply force on axle to turn the wheel.

Many many thanks.

2. Apr 7, 2015

### mathman

You need to supply some context.

3. Apr 7, 2015

4. Apr 7, 2015

### SteamKing

Staff Emeritus
How are you going to use just a wheel by itself if you don't have at least a short axle:

1. about which the wheel rotates
2. which can be affixed to the vehicle which rolls on the wheel(s)?

Otherwise, you go everywhere like this:

5. Apr 7, 2015

### LogU16

Thanks for this pic, Berkeman. Could you please explain it a bit? it will be a great help.

6. Apr 7, 2015

### Staff: Mentor

Just google Car Differential. If you have specific questions about what you read, post them in this thread with links to the reading, and we can help out with your specific questions...

7. Apr 7, 2015

### rcgldr

The closest analogy to using a wheel only is a "walking globe", where a person stands on a globe (ball) and positions their center of mass a bit off center to cause the ball to move, and they reposition their center of mass by walking in the opposite direction to control the speed and/or stop the ball.

A simple example of applying a torque to an axle to turn a wheel is a walking spool, similar to ones used to hold telephone wires. The principle is the same as the walking globe, but it's easier to control.

Last edited: Apr 7, 2015