Follow a spinning skater's energy

Exercise and reference answers

Questions

1. Answer

   18

   Question

   A skater spins at 3 rad/s with moment of inertia 4 kg m squared. Her kinetic energy in joules?

2. Answer

   72

   Question

   She pulls her arms in to 1 kg m squared, conserving angular momentum. Her kinetic energy now, in joules?

3. Answer

   54

   Question

   How many joules did her own muscles supply while she pulled her arms in?

Instructions

Key in each energy for the spinning skater as a whole number of joules.

Explanation