Collision between ball and stick

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AI Thread Summary
A 0.58 kg glob of clay strikes a 1.62 kg bar on a frictionless table, sticking to it after impact. The final speed of the center of mass is calculated to be 1.63 m/s using conservation of momentum. The discussion shifts to determining the angular speed of the bar/clay system post-impact, with participants suggesting the use of conservation of angular momentum. It is noted that the initial angular momentum is zero since the bar is at rest before the impact. The conversation emphasizes the importance of identifying the center of mass for the system to solve for angular momentum before and after the collision.
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Homework Statement


On a frictionless table, a 0.58 kg glob of clay strikes a uniform 1.62 kg bar perpendicularly at a point 0.18 m from the center of the bar and sticks to it. If the bar is 0.70 m long and the clay is moving at 6.20 m/s before striking the bar, what is the final speed of the center of mass?
A=1.63m/s

At what angular speed does the bar/clay system rotate about its center of mass after the impact?
A=?

[PLAIN]http://img217.imageshack.us/img217/616/prob21a.gif


Homework Equations



Not sure

The Attempt at a Solution



I solved for the final speed of the center of mass using conservation of momentum, but i am lost on the 2nd part. I know the center of mass changes when the clay is attached to the bar, but I am not sure how i would use that to solve the question.
 
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Hi juggalomike! :wink:

Use conservation of angular momentum …

what do you get? :smile:​
 
tiny-tim said:
Hi juggalomike! :wink:

Use conservation of angular momentum …

what do you get? :smile:​

If i using conservation of angular momentum, which is Ii*Wi=If*Wf the initial side will be 0 because initialy it has no angular velocity?
 
Hello juggalomike,

Think about what is the center of mass of the system (the system being the combination of bar and glob) immediately before impact. Using that point as the center of mass, what is angular momentum (before impact) associated with the bar? And the glob? :wink:
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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