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.

the bal will not change its velocity.

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

where is unknown. because the position is parabolic, there is symmetry about the midpoint at , and we know that

so that the position function is

which means the velocity is

then the total distance traveled is

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at and ends at , so its displacement is 0.