# Homework Help: Change of speed of a car turning in circles

1. Jan 5, 2014

### alingy1

My textbook says : "The friction force on a car turning a corner does no work."

I agree somewhat. However, if there is no work, there is no change of speed, aka no change of kinetic energy.

How can a car in a real-life stop if it is doing perfect circles with forces pointing towards the center of those circles?

Is there another component of friction in play?

2. Jan 5, 2014

### alingy1

I forgot to mention: I imply that the car driver is neither pushing the gas pedal nor the brakes!

3. Jan 5, 2014

### Tanya Sharma

Yes...There has to be a component of friction in tangential direction providing the required deceleration (i.e causing the speed to reduce ) .

4. Jan 5, 2014

### ehild

The car does not stop when turning a corner - it moves along a circle.

Its velocity changes direction, but not magnitude. The speed stay constant.

When a car stops, some force is applied parallel to its velocity, opposite to it.

ehild

5. Jan 5, 2014

### ehild

Tania beating me again

ehild

6. Jan 5, 2014

### Tanya Sharma

I saw you typing but didn’t notice you were replying to this thread