A local ice hockey team has asked you to design an apparatus for measuring the s

Question

A local ice hockey team has asked you to design an apparatus for measuring the speed of the hockey puck after a slap shot. Your design is a 2.00-m-long, uniform rod pivoted about one end so that it is free to rotate horizontally on the ice without friction. The 1.30-kg rod has a light basket at the other end to catch the 0.163-kg puck. The puck slides across the ice with velocity v (perpendicular to the rod), hits the basket, and is caught. After the collision, the rod rotates. If the rod makes one revolution every 0.736 s after the puck is caught, what was the puck's speed just before it hit the rod? Express your answer with the appropriate units.

Explanation / Answer

here,

time period of rod , T = 0.736 s

angular speed , w = 2 * pi /T

w = 8.53 rad/s

l = 2 m

mass of rod , mr = 1.3 kg

mass of puck , mp = 0.163 kg

let the initial speed of puck be u

using conservation of angular momentum about the pivot point

mp * u * l = ( mr * l^2 /3 + mp * l^2) * w

0.163 * u * 2 = ( 1.3 * 2^2 /3 + 0.163 * 2^2) * 8.53

u = 62.4 m/s

the initial speed of the puck is 62.4 m/s

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