- #1

WonderKitten

- 4

- 1

Hi, I have the following problem:

A homogeneous disc with M = 1.78 kg and R = 0.547 m is lying down at rest on a perfectly polished surface. The disc is kept in place by an axis

A particle with m = 0.311 kg and v = 103 m/s, normal to the disc's surface at the point of contact.

After the collision, the particle stays stuck to the impact point

What's the angular velocity of the system after the collision?

It might be a bit confusing as I had to translate the problem, sorry about that. I'm not entirely sure if the disc is rotating on it's x-axis or z-axis (y-axis?), and by the particle being 'normal to the disc's surface' I think it means it's perpendicular to the disc? Not sure what I should do with this information.

So, since the axis of rotation isn't on the center of mass:

I (disc) = MR²/2 + MR² = 3MR²/2

The distance from O' to O: (using pythagoras)

r = 0.774

I (particle) = mr²

Ip * vR = - (Id + Ip) * wf

solving for wf and substituting the values I get wf = -10.6.

This is wrong, apparently. Not sure why, I'm out of ideas. Could someone help me out? Thanks!

A homogeneous disc with M = 1.78 kg and R = 0.547 m is lying down at rest on a perfectly polished surface. The disc is kept in place by an axis

**O**although it can turn freely around it.A particle with m = 0.311 kg and v = 103 m/s, normal to the disc's surface at the point of contact.

After the collision, the particle stays stuck to the impact point

**O'.**What's the angular velocity of the system after the collision?

It might be a bit confusing as I had to translate the problem, sorry about that. I'm not entirely sure if the disc is rotating on it's x-axis or z-axis (y-axis?), and by the particle being 'normal to the disc's surface' I think it means it's perpendicular to the disc? Not sure what I should do with this information.

So, since the axis of rotation isn't on the center of mass:

I (disc) = MR²/2 + MR² = 3MR²/2

The distance from O' to O: (using pythagoras)

r = 0.774

I (particle) = mr²

Ip * vR = - (Id + Ip) * wf

solving for wf and substituting the values I get wf = -10.6.

This is wrong, apparently. Not sure why, I'm out of ideas. Could someone help me out? Thanks!

**[Moderator's note: Moved from a technical forum and thus no template.]**
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