Question

there are many types of energy. one type is kinetic energy, which is the energy an object has when it is moving.
read the passage about a bike ride. think about the kinetic energy of the person riding the bike.

ellen was training for a bike race. one afternoon, she grabbed her helmet and took her bike out to the street. she got on the bike and started to pedal, pushing hard to start moving forward.

which of the following is better evidence that ellen’s kinetic energy changed?
when ellen started pedaling her bike, she began moving along the street.
when ellen got on her bike, her feet were no longer touching the ground.

Explanation:

Kinetic energy depends on an object's motion (speed and mass, here mass is constant for Ellen). The first option shows Ellen began moving (change in motion, so kinetic energy changed as she started moving from rest). The second option (feet not touching ground) doesn't relate to motion (kinetic energy) change, just her position on the bike. So the first statement is better evidence.

Answer:

When Ellen started pedaling her bike, she began moving along the street.