- #1
Redfire66
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Homework Statement
A puck of mass 82.0g and radius 4.09cm slides along an air table at a speed of v = 1.59m/s. It makes a glancing collision with a second puck of radius 6.97cm and mass 130g (initially at rest) such that their rims just touch. The pucks stick together and spin after the collision (b). What is the angular momentum of the system relative to the center of mass?
Homework Equations
Angular Momentum (Conserved)
Center of Mass
The Attempt at a Solution
I got the first part, using center of mass relative of the larger mass and speed of the smaller mass giving me an initial value of angular momentum during the first part of collision of 8.84×10-3 kg*m^2/s. (This is confirmed to be correct)
However the second part I'm having trouble figuring out the moment of inertia. I thought that since angular momentum is conserved, I would have L/I = ω
And I = Icm (relative to smaller mass) + m1r1^2 + Icm(relative to larger mass) + m2r2^2
Where Icm = 1/2 mr^2 (r is the distance from the center of mass relative to each mass)
According to the textbook the answer should be about 8.85rad/s however I keep getting 9.00rad/s
Not really sure what I'm doing wrong, is my perspective on center of mass wrong? Since I can't think of another way the center of mass can be set a distance of. Also I'm not really sure about the parallel axis theorem if you could also explain how it comes into play when creating a formula for moments of inertia
Thanks