# Cars

How does a car go on the ground?
Which forces are acting on the wheels of the car so that it goes forward?
What are the name of these forces and in which direction do they act on the wheels of the car?

 Starman Posts: 1,364, Reputation: 794 - #2 Jun 4, 2003, 10:15 PM
Re: cars
A car motor has pistons inside cylinders.

In some cars Gasoline vapor is introduced into the cylinders by a carburetor.

Each cylinder has a spark plug.

As the vapor enters the cylinder the spark plug fires an electrical spark.

This causes the gasoline vapor to explode.
The explosion moves the piston upward within the cylinder.

The up and down motion of the pistons is transmitted via gears to the wheels and is converted to the rotary motion which moves the car.
 Dr._Ephemeron Posts: 22, Reputation: 1 New Member #3 Jun 28, 2003, 10:38 PM
Re: cars
Q: how does a car go on the ground?

A: Mine goes very well, how 'bout yours?

Q: which forces are acting on the wheels of the car so that it goes forward?

A: Frictional force from the ground pushes it forward.

Q: what are the name of these forces and in which direction do they act on the wheels of the car?

A: The frictional force pushes forward on the bottom of the weel.

Of course from inside the car, it looks like the cars wheels are pushing the ground backwards underneath it. ;D

Bonus Question

From an Earth frame of reference:

1. How fast is the point at the bottom of the wheel moving?

2. How fast is a point on the top of the wheel moving?
 Dr._Ephemeron Posts: 22, Reputation: 1 New Member #4 Jun 29, 2003, 08:33 AM
Re: cars
Quote:
 author=Starman link=board=physics;num=1053003387;start=0#1 date=06/04/03 at 22:15:22]A car motor has pistons inside cylinders. In some cars Gasoline vapor is introduced into the cylinders by a carburetor. Each cylinder has a spark plug. As the vapor enters the cylinder the spark plug fires an electrical spark. This causes the gasoline vapor to explode. The explosion moves the piston upward within the cylinder. The up and down motion of the pistons is transmitted via gears to the wheels and is converted to the rotary motion which moves the car.

Actually, the gasoline vapor does not "explode", it combusts. If it explodes, you will shortly have some serious piston and valve problems.

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