Fact 1: Friction causes an object to lose energy.

Fact 2: With less energy, the electron slows down.

Given the two facts above, answer the question "What causes an object to slow down?" with the following options: 
- sweating
 - hormones
 - quadriceps
 - smooth surfaces
 - electrically
 - friction
 - speed
 - lack of friction


 

      friction   