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The 2 kg sphere with negligible radius is moving at 10 m/s when it strikes the
stationary unconstrained uniform 4 kg bar and sticks to it.
What is the bar’s
angular velocity after the impact?
What is the kinetic energy of the system
after the impact?
Assume the horizontal surface is frictionless.
Deals with impacts, so probably need impulse
momentum.
A rigid body, so will definitely need to do angular
– lets start
there, then we’ll see if we need to do linear too.
What point should we use?
How can we relate
ϖ
and v
A
?
Still need another equation – how about linear momentum?
We can group our three equations, then do linear algebra to get v
A
, v
B
, and
ϖ
Use these numbers to determine kinetic energy before and after impact.
Nm
Reflection:
You lose over half the
kinetic energy in the impact.
The center of the bar will also
move, so can’t just say that
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 Spring '05
 staff
 Strain

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