Rotational Motion and Energy

A solid  metal bar is at rest on a horizontal frictionless surface. It is free to rotate about a vertical axis at the left end. The figures show forces of different magnitudes that are exerted on the bar at different locations. In which case does the bar's angular speed about the axis increase at the fastest rate?

• A
• B
• C
• D

Two equal forces do W Joules of work on cylinder (I=¹/₂mr²) and a hoop (I=mr²) of the same radius and same mass.  What is the ratio of the total kinetic energy of the cylinder to the total kinetic energy of the hoop after this work has been done?

• 1:1
• 1:2
• 2:1
• 1:4

Tags

NGSS.HS-PS2-1

NGSS.HS-PS3-1

A cylinder (I=¹/₂mr²) and a hoop (I=mr²) of the same radius and same mass are traveling at the same angular velocity (ω).  What is the ratio of the angular momentum of the cylinder to the angular momentum of the hoop?

• 1:1
• 1:2
• 2:1
• 1:4

A cylinder (I=¹/₂mr²) of mass M and radius r rolls with a linear velocity v.  What is its angular momentum?

• Mv
• Mv/r
• Mrv/2
• Mrv

When a rigid object rotates about a fixed axis, what is true about all the points in the object? 

• They all have the same tangential acceleration.
• They all have the same angular speed.
• They all have the same tangential speed.
• They all have the same radial acceleration.

The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest moment of inertia when rotated about an axis through point P?

• A
• B
• C
• D

Which has greater linear speed, a horse near the outside rail of a merry-go-round or a horse near the inside rail?

• the inside horse
• the outside horse
• Neither

Which has greater angular speed, a horse near the outside rail of a merry-go-round or a horse near the inside rail?

• The inside horse
• The outside horse
• Neither - they both have the same angular speed

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.

Tags

NGSS.HS-ETS1-3

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.

Tags

NGSS.HS-PS2-4

NGSS.HS-ESS3-1

NGSS.HS-ESS3-5