1. An object initially at rest falls from a height H until it reaches the ground. Two of the following energy bar
charts represent the kinetic energy K and gravitational potential energy Us of the object-Earth system at
two positions. The first position is when the object is initially released, and the second position is when the
object is halfway between its release point and the ground. Which two charts could represent the mechanical
energy of the object-Earth system? Select two answers.

change tension

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

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.