# Homework Help: Physics ball speed

1. Feb 14, 2006

### cutie05

Consider the identical balls released from rest on Tracks A and B as shown. When they reach the right ends of the tracks, which will have the greater speed?
Will The ball on track B will have the greater speed.
There is not enough information to decide.
Both will have the same speed.
The ball on track A will have the greater speed.

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2. Feb 15, 2006

### BobG

Tough to say, since the picture is awaiting approval. The general approach should use the idea that energy is conserved. Any loss of potential energy is compensated for by an increase in kinetic energy. Your change in potential energy is reflected in the change in height (PE = mgh). Your change in kinetic energy is reflected in the change in velocity (KE=1/2 mv^2). If you lose height, the velocity has to increase. If you gain height, the velocity has to decrease.

3. Feb 16, 2006

### civil_dude

Since the track lengths are different, you have know about friction. Do you ignore it?

4. Feb 16, 2006

### Gramma2005

Well, since the tracks both start and end at the same heights, the speed must be the same if they both start at the same speed. Using the potential energy = mgh, and the mechanical energy formula K_f + U_f = K_i + U_i.

5. Feb 16, 2006

### Pengwuino

You need to know if the track has friction