Rotational Inertia

Is torque independent of the location of the origin?

• Yes, always.
• Yes, as long as the origin is either in the center or on one end.
• No, you always need to specify the origin.

Suppose you are designing an engineless car for a downhill coasting race.  What type of wheels would be the best?

• Solid disks.
• Hoops.
• Hollow cylinders.
• Diamond encrusted triangles.

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NGSS.HS-ETS1-2

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Stars originate as large bodies of slowly rotating gas.  Because of gravity, these clumps of gas slowly decrease in size.  What happens to the angular speed of the start as it shrinks?

• It rotates faster.
• It rotates slower.
• It starts to accelerate in the forward direction.
• The rotation rate stays the same.

As global warming occurs over the next century, the polar ice caps will start to melt ant the water will be distributed closer to the equator.  How will this change the Earth's moment of inertia?

• It would increase.
• It would decrease.
• It would stay the same.

What would happen to the length of one day if Earth's moment of inertia were to increase?

• The day would be longer.
• The day would be shorter.
• The day would stay the same.

A mouse is initially at rest on a horizontal turntable mounted on a frictionless vertical axle.  If the mouse begins to walk clockwise around the perimeter, what happens to the turntable?

• The turntable will remain stationary.
• The turntable will rotate clockwise too.
• The turntable will rotate counterclockwise.
• The turntable will only move if the mass of the mouse is greater than the mass of the turntable.

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NGSS.HS-PS2-1

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Three homogeneous ridged bodies -- a solid shere, a solid cylinder, and a hollow cylinder -- are placed at the top of an incline.  If all are released from rest at the same elevation and rolls without slipping, which reaches the bottom first?

• The solid sphere.
• The solid cylinder.
• The hollow cylinder.
• They will all arrive at the same time.

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NGSS.HS-PS3-1

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A merry-go-round spins freely when Diego moves quickly to the center along a radius of the merry-go-round. As he does this, it is true to say that

• the moment of inertia of the system increases and the angular speed increases.
• the moment of inertia of the system decreases and the angular speed remains the same.
• the moment of inertia of the system decreases and the angular speed decreases.
• the moment of inertia of the system decreases and the angular speed increases.

A uniform solid cylinder with a radius of 10 cm and a mass of 3.0 kg is rotating about its center with an angular speed of 33.4 rpm. What is its kinetic energy?

• 0.092 J
• 17 J
• 1.1 J
• 0.18 J

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NGSS.HS-PS3-1

The drive chain in a bicycle is applying a torque of 0.850 N ∙ m to the wheel of the bicycle. You can treat the wheel as a thin uniform hoop (or ring) with a mass of 0.750 kg and a radius of 33.0 cm. What is the angular acceleration of the wheel?

• 10.4 rad/s2
• 3.43 rad/s2
• 5.20 rad/s2
• 1.06 rad/s2

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NGSS.HS-PS2-1