You just finished playing a record and hit the switch off. It is still spinning

Question

You just finished playing a record and hit the switch off. It is still spinning at 33.0 RPM, when you drop a piece of clay onto it, a distance of 3.50 cm from the center.

a)The record is a disk with a radius of 6.0 cm and a mass of 0.015 kg. What is its moment of inertia before the clay lands on it?

b) What is the record%u2019s original angular momentum before the clay lands on it?

What is its original rotational kinetic energy?

c) When the clay is dropped onto the record, it can be treated as a point particle.

What is the moment of inertia of the clay/disk system?

d) What is the final angular velocity of the record and clay after the clay lands?

e) What is the angular momentum and rotational energy after the clay landed on the disk?

Explanation / Answer

a) I = 1/2mr^2 = 0.5*0.015*0.06*0.06 = 0.000027 kg-m^2

b) L = Iw =0.000027*33*2*pi/60 = 0.0000933

c) I = 0.000027+1*0.035*0.035 = 0.001252 kg-m^2

d) w = 0.000027*33/0.001252 = 0.71 RPM

e) L = 0.0000933 ( as L is conserved)

KE = 1/2*I*w^2 = 0.5*0.001252*0.71*0.71*4*pi*pi/(60*60) = 0.00000346

Related Questions

Navigate

• Browse (All)
• Browse Y
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.