# Inelastic collision angular acceleration problem

1. Nov 16, 2012

### llisle39

Having problem with task b). Any suggestions?

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2. Nov 16, 2012

### Staff: Mentor

Show what you've done so far and where you are stuck. What physics principles or equations do you think might be relevant here?

3. Nov 17, 2012

### llisle39

1. A door gets hit by a lump of clay with mass m=0.50 kg. The lump of clay has a velocity of v=10 m/s and hits the outer edge of the door at a right angle lodging itself in the door (See picture)

In task a) we used the formula (I=1/3*M*r^2) and calculated the inertia being 7 kgm^2/s.

In task b) we are looking for the angular acceleration. So far we have found the angular velocity (w) but are having difficulties finding the angular acceleration (alpha) We tried to combine the inertia for the door and the lump of clay. And we have tried to use the formula for angular momentum saying that La = Lb

4. Nov 17, 2012

### Staff: Mentor

I don't see how you can determine the angular acceleration of the door during the collision with the data given, if that's what they are asking. After the collision should be easy though: What forces act on the door creating a torque?

Perhaps they meant to ask for the angular velocity after the collision, not the acceleration?

Tell me what parts a and c ask for.

5. Nov 17, 2012

### llisle39

We are looking for the angular acceleration after the collision. Task a asks for the inertia. This was no problem. Task c asks for the remaining kinetic energy after the collision :-)

6. Nov 17, 2012

### Staff: Mentor

Angular acceleration is the rate at which the angular velocity changes. I strongly suspect that they meant to ask for the angular velocity of the door after the collision, not the acceleration.