Question

A cyclist free-wheels from the top of a hill, gathers speed going down the hill, apply his brakes and eventually came to rest at the bottom of the hill. Which one of the following energy changes take place?

• A. Potential to kinetic to heat energy
• B. Kinetic to potential to heat energy
• C. Chemical to heat to potential energy
• D. Kinetic to heat to chemical energy

Answer 1

The correct option is A Potential to kinetic to heat energy

Considering ground as zero potential
Initially $E=U+K=U+0=U$
Finally $E=U+K=0+0=0$
So, initially it had some potential energy, it was converted to kinetic energy by gaining speed, it finally became zero so energy must have been lost as heat while applying brakes.