you will have to turn in the worksheet. The remaining time will be spent going o
ID: 1585711 • Letter: Y
Question
you will have to turn in the worksheet. The remaining time will be spent going over the answers. Question 1: You're listening to a great LP record on your turntable (LP means 33% revolutions per minute). Midsong, a large bug of mass 10 g lands and sticks (ie. "collides") onto the record two-thirds the distance from the center to the edge of the record. If the record has mass 100 g and has a diameter of 30 cm, how fast will the record be spinning after the bug has landed? (Approximate the record as a spinning disk) - 10g l00, Question 2: If we apply a constant torque of 0.118 Nm to a thin rod of length 1.0 m and mass o0.5 kg causing it to rotate from rest about the middle, how many revolutions will one end of the rod make in 10 seconds?Explanation / Answer
Given that
m1 = 100 g
R = d/2 = 30/2 = 15 cm = 0.15 m
m2 = 10 g
wi = 33.5 rpm = 33.5*(3.142/30) = 3.51 rad/s
initial moment of inertia is I1 = 0.5*m1*R1^2 = 0.5*100*10^-3*0.15^2 = 0.001125 kg-m^2
Final moment of inertia is I2 = 0.001125+ (m2*r2^2) = 0.001125+(10*10^-3*(2*0.15/3)^2) = 0.001225 kg-m^2
then
using law of conservation of angular momentum
I1*w1 = I2*w2
0.001125*3.51 = 0.001225*w2
w2 = rad/s = 3.22*(30/3.142)= 30.75 rpm
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