# The Naked Scientists Forum

### Author Topic: What are the forces on a car travelling in a circle?  (Read 7142 times)

#### Geezer

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##### What are the forces on a car travelling in a circle?
« Reply #25 on: 11/07/2010 21:14:03 »
I go and stand in corner and don cap of ignorance

No need for that!

BTW - here's a slight modification that might help.

Imagine we build a car that is designed to only travel in a circle of a particular radius. We set it up so that all the wheels are more or less tangential to the path they follow. (I suppose we could achieve the same effect with front and rear wheel steering.)

#### Erik Moeser

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##### What are the forces on a car travelling in a circle?
« Reply #26 on: 15/07/2010 18:35:50 »
A vehicle is traveling in a straight line, say a space vehicle, or an efficient rolling one on a huge flat surface, like Libya only smoothly paved.

The one in space requires no power to keep going.  The one on the desert flat needs some power to overcome the air and mechanical friction, however little or much that might be.

I have mounted on the right side either vehicle a jet thruster, pointed at a 90 degree angle away from the body.  When I fire it gently off, each of the vehicles begins a turn to the left.  By definition each is now "registering" lateral g force since the formula for that only includes time and radius.  I am inputting energy, power, or whatever we call it, the vehicle is turning.  When I stop, the vehicles return to traveling in a straight line.   If the jet left in a continuous burn, both keep circling.  The more I ramp up the power the shorter the radius becomes and the more lateral g involved.  Which leads me to the (premature?) conclusion that it takes energy to have lateral g.

I am not far from imagining that work is being done by a circling vehicle, in that it is always accelerating away from the straight and natural course.

What am I overlooking?

#### syhprum

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##### What are the forces on a car travelling in a circle?
« Reply #27 on: 15/07/2010 21:04:25 »
There is no need for a jet engine producing a thrust, angled tyres will produce the required thrust without consuming any power apart from frictional losses.
If you were operating in space the jet thruster would be the only way to do it but on a road surface tyres will suffice.

#### Geezer

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• "Vive la résistance!"
##### What are the forces on a car travelling in a circle?
« Reply #28 on: 15/07/2010 22:41:17 »
There are many ways to produce the necessary centripetal force. A jet thruster could be one of them.

However, just because they produce a force and consume energy, it does not mean they do work. The net amount of work done during a 360 degree circuit is zero.

As Syhprum says, tires will work just as well, and they'll consume a lot less energy.

#### The Naked Scientists Forum

##### What are the forces on a car travelling in a circle?
« Reply #28 on: 15/07/2010 22:41:17 »