# Centripetal Force.

1. Sep 6, 2007

### Energize

I have to explain the argument, why the centripetal force must be radial and towards the centre, rather than away. I have just started circular motion and have no idea how to explain this sort of thing, I don't even understand the question!

2. Sep 6, 2007

3. Sep 6, 2007

### learningphysics

Draw a picture... an object moves in a circle at a constant speed. Draw the velocity vector at a point... the draw a velocity vector after it moves a tiny distance on the circle... Draw $$\vec{v2}-\vec{v1}$$... see which direction it points? That's approximately the direction of acceleration.

Another thing to consider... the centripetal force doesn't change the speed... that makes it necessary for the force to be radial... think of work and energy to figure out why...