Skater 4

A figure skater is spinning on ice with their arms extended. When they pull in their arms, their rotational kinetic energy increases. What is the source of this energy?

A) Work

B) Heat

C) Thermal energy

D) Potential energy

E) Chemical energy

F) Other or can't tell

Solution: E. It is not correct to attribute this increase in kinetic energy to work because the forces doing work are inside the person. The kinetic energy comes from the person's metabolic processes, a transformation of internal chemical energy into rotational kinetic energy (and some thermal energy as the transformation isn't 100% efficient).

If we look further back, then we can assert that the energy begins as nuclear energy from the sun (which is eventually transmitted and transformed into chemical energy in plants).