Energy systems

Energy Systems

Discussing Two Issues

Here are ideas for discussing these two issues:

1. The wheels won’t turn.

2. The wheels fall off the axle.

If something won’t move when you push it or let it go on a ramp, friction is preventing it from going. You allow the wheels to roll by reducing friction. Ask:

For the car to roll, which parts need to be able to turn?
Which parts should not be able to turn?
How can you allow one part to turn, while the other part doesn’t?

Develop the idea that there are two ways to allow the wheels to turn:

The wheels can be fixed to the axles, but then the axles have to be able to turn freely under the body, i.e., they can’t be fastened to the body; or
The wheels can be loose on the axles, allowing them to rotate freely. This allows the axles to be fastened to the body, but then there needs to be something to stop the wheels from falling off.
Lead a discussion about how to solve the problems of either:
Allowing the axles to rotate
Keeping the wheels on the axles.