Which is harder to spin up?

Exercise and reference answers

Questions

1. A

   Hoop about its own axis

   B

   Solid disk, same axis

   Higher value

   Hoop about its own axis

2. A

   Solid sphere at its centre

   B

   Hollow shell, same centre

   Higher value

   Hollow shell, same centre

3. A

   Solid disk, central axis

   B

   Solid sphere at its centre

   Higher value

   Solid disk, central axis

4. A

   Hollow hoop, central axis

   B

   Solid sphere at its centre

   Higher value

   Hollow hoop, central axis

5. A

   Mass packed at the axis

   B

   All mass out at the rim

   Higher value

   All mass out at the rim

6. A

   Point mass at radius R

   B

   Solid disk of radius R

   Higher value

   Point mass at radius R

Instructions

Tap the one with the larger moment of inertia. Each pair has equal mass and equal radius.

Explanation