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Kinematics and angular speed of a collision between a rod and puck

  • #1
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6

Homework Statement:

A rod of mass 1.8 kg and length 3.3 m lies motionless on the frictionless ice, pointing North-South. A glue-covered hockey puck of mass 0.6 kg slides towards the rod at a speed of 8 m/s heading East.
What is the total kinetic energy of these objects?

The puck collides with the rod at the very middle of the rod, and sticks there.

What is the final linear speed of the combined object after the collision?

What is the final angular speed of the combined object after the collision?

What is the total kinetic energy of these objects now, after the collision?

Relevant Equations:

KE= (1/2) (mass)(velocity)^2
initial total KE= (1/2)(0.6kg)(8m/s)^2 = 19.2J
(0.6kg)(8m/s) = (0.6kg+1.8kg)(vf)
vf= 2m/s
final KE= (1/2)(0.6kg+1.8kg)(2m/s)^2 = 4.8J
I tried to use linear speed=angular speed * radius : thus
2m/s= angular speed * (3.3m/2)
angular speed= 1.2 rad/s
Apparently that is wrong.
 

Answers and Replies

  • #2
PAllen
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Can you describe what angular speed is, rather than just a formula. That should be a big hint, if you think about the problem description.
 
  • #3
123
6
0 rad/s
 
  • #4
haruspex
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