Engineering Solving Momentum Conservation Problems: Tips & Tricks

[greg_rack]

Homework Statement

DIAGRAM ATTACHED BELOW:
Determine the height $h$ of the bumper of
the pool table, so that when the pool ball
of mass $m$ strikes it, no frictional force
will be developed between the ball and
the table at A. Assume the bumper exerts
only a horizontal force on the ball.

Relevant Equations

Conservation of momentum, planar rigid body kinetics

Hello guys,

could someone give me a small hint to get me started on attempting this problem? I really cannot figure out how to relate conservation of momentum to the fact that there shouldn't be friction... does it have something to do with the so-called "sweet spot" of the ball?
But then, where's the correlation with $L$.

With the latter, the only thing I can come up is, with subscript $_i$ for init. conditions:
$$F_{bumper}\Delta t +F_{friction}\Delta t_2=mv_{Gi} \rightarrow
F_{bumper}\Delta t=mv_{Gi}$$
... but it doesn't seem to take me anywhere

 

[BvU]

something to do with the so-called "sweet spot" of the ball?

It certainly does ! Google for a derivation showing the details ...

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