#### Transcript of LPH 105 W15 8.8-10

Angular momentum

Impulse momentum corollary

conservation of momentum

Linear to angular momentum

" two children each with a mass of 25 kg sit on the outside edge of a 2.0 m radius merry go round which has a moment of inertia of 450 kg m^2. If it is initially moving at a speed of 2.5 rad/s, what will be the angular velocity if the kids move to the very center of the merry go round?

A uniform disk turns at 3.3 rev/s around a frictionless central axis. A nonrotating rod, of the same mass as the disk and length equal to the disk's diameter is dropped on the freely spinning disk. they then turn together around the axis with their centers superposed. What is the angular frequency in rev/s of the combination?

A boy with a mass of 35 kg runs with a speed of 4 m/s towards the outside edge of a stationary merry go round having a mass of 150 kg and radius of 2 m. He jumps on tangentially and lands on the outside edge, what is his angular velocity once on the merry go round?

A 0.75 kg, 1.5 m long rod is attached to a frictionless table by a nail at its center of mass and allowed to rotate freely. A .25 kg ball of clay is thrown with a speed of 25 m/s , sticks to one end of the rod. What is their angular velocity after the collision?

**How long would it take a 2.5 N m torque acting tangentially to the edge of a 1.5 m radius 25 kg disk, to reach the angular velocity of 95 rad/s?**

A 200 g toy car is placed on a narrow 60 cm diameter track with wheel grooves that keep the car going in a circle. The 1.0 kg track is free to turn on a frictionless, vertical axis. The spokes have negligible mass. After the car's switch turned on, it soon reaches a steady speed of 0.75 m/s relative to the track. What then is the track's angular velocity in rpm?

3.61 rad/s

1.98 rev/s

.64 rad/s

16.7 rad/s

1070 s

3.98 rpm

"Just need more practice with determining if a problem is kinematic, dynamic, energy, or momentum. What confused me a little bit is that we can do problems in kinematic and energy.... or some other kind of combo."

"I don't understand the last question of the pre quiz. Could you go over it in class?"

"I feel lost, and I am trying to figure out things and exercises that I can do to better practice this stuff. Any ideas?"

"If a disk of mass 2 kg is rotating at a rate of 3 rad/s and has a radius of 1.5 m. What is its angular momentum (answer should look like '8.7 kg m^2/s')."

"RHR"

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