Question

Imagine holding a mic at a height above the ground. It is released and falls toward the ground.

Ignoring air resistance or friction, which of the following must be true?

(3 points)
Responses

Before it falls, all of its energy must be potential energy
Before it falls, all of its energy must be potential energy

At the end of its fall, all of its energy must be converted to kinetic energy
At the end of its fall, all of its energy must be converted to kinetic energy

During its fall, the combination of its kinetic and potential energy must equal the amount of potential energy with which it started
During its fall, the combination of its kinetic and potential energy must equal the amount of potential energy with which it started

Total energy = Kinetic Energy + Potential Energy
Total energy = Kinetic Energy + Potential Energy

All of the above

Answer 1

All of the above.

Reason: Ignoring air resistance and friction, mechanical energy is conserved. While held at rest the mic has no kinetic energy so its mechanical energy is all gravitational potential. As it falls that potential is converted into kinetic, and just before impact the kinetic energy equals the initial potential. At every instant KE + PE = constant (the initial PE). (This assumes we ignore other forms of energy like heat, sound, chemical, etc.)