Alift (elevator) is operated by an electric motor. it descends from the 10th floor to the 2nd floor at a constant speed. what is the main energy transformation during this journey?

#1
gravitational potential energy → kinetic energy.

#2
electrical energy → kinetic energy.

#3
kinetic energy → thermal energy.

#4
electrical energy → thermal energy.

#4 Electrical energy to thermal energy

Explanation:

You clue there is constant speed, this means that the lift is not accelerating. So if that is the case, the lift is experiencing a resistive force against gravity. The one doing exerting the resistive force is the motor, which runs on electrical energy. Resistive force transforms into heat, so that makes it thermal energy. And so, the answer would be the last case.

no. dot product   =0 when vecs at right angles