# Change of Direction

1. Oct 9, 2007

### Drifter009

Is is possible when two objects have one interaction, that one object experience only a change of direction and no change in speed?

It seems possible for two objects to have an interaction where there is no change of direction. (Each object has no spin and they are on a co-linear path.) But, I can't think of a way to see an interaction, where one object has a change of direction but no change of speed.

Last edited: Oct 9, 2007
2. Oct 9, 2007

### Shooting Star

Change of direction implies change in velocity, since velocity is a vector.

I hope you didn't mean speed when you said velocity. In that case, of course it's possible.

Which class are you in?

3. Oct 9, 2007

### Drifter009

Yes, I mean speed in place of velocity. I will edit it to stop the confusion.

Would it be easy to explain, I am only taking conceptual physics. So, a non-mathematical explanation would be best for me.

This is why I can't think of it any other way:

In order for a mass to change position in a non-linear way, a change in speed must occur which is relative to the original linear path the mass was moving along (or at rest with). So, a change in direction always accompanies a change in speed.

Last edited: Oct 9, 2007
4. Oct 9, 2007

### Claude Bile

Circular motion, such as the Earth orbiting the sun is an example of the speed remaining constant while direction changes.

Claude

5. Oct 10, 2007

### Drifter009

I thought the Earth's velocity changes, due to an elipitical path. But, if it were circular I still have a problem. If I choose one tangent along the circular path in which the Earth moves and measure the speed in that direction as the Earth passes. The next moment, the Earth has changed direction. From the new tangent, the speed is the same, but from the old force vector, the speed has decreased.

6. Oct 10, 2007

### Shooting Star

(I am trying my best to understand you and answer.)

The component of the new velo along the old tangent has decreased, but an additional component of the new velo normal to the old tangent has been introduced. The magnitude of the vector sum of these two will remain the same, thus keeping the speed the same at both positions.

7. Oct 12, 2007

### Claude Bile

I don't get the bold part, an object can only have one speed. What I think you are doing is looking at the velocity component in a particular direction. Yes the velocity changes, no question, but the speed does not.

Claude.