# Ball and a step

1. Dec 5, 2004

### Feynmanfan

What is the minimum velocity the ball should have in order to go up the step, considering it doesn't slip. Here's a picture.

I would be grateful if you could give me a hint.

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2. Dec 6, 2004

### Feynmanfan

is it that i didn't explain the problem correctly?

3. Dec 6, 2004

### Clausius2

Your picture is very diffuse. Anyway, If I were you, I will take the momentum (torque) equilibrium at the point of contact between the ball and step. At that point

$$\sum F_i r_i >0$$ in order to enhance the turning of the ball around the wedge.

Also, you should try with energy conservation (kinetic--->potential) if you want a gross estimation.

4. Dec 6, 2004

### arildno

You need to break this up a bit:
You have been told that the ball will NOT slip at the corner; evidently this must mean that the velocity of the contact point of the ball is ZERO, throughout the motion (after contact is has been made)

A) The collision phase:
The angular momentum of the ball with respect to the corner must be conserved throughout the collision (why is that).
This gives you the resultant angular velocity just after the collision, in terms of the initially given parameters.
B) Post-collision phase:
Only gravity does work on the system here, due to the no-slip condition.
Hence, mechanical energy is conserved.

Good luck&good constitution day to all Spaniards!..