Exercice 20 : Un ballon sous l'eau. Anne s'amuse à maintenir un ballon sous l'eau pour le relâcher et le voir jaillir hors
de l'eau. On s'intéresse aux forces qui s'exercent sur le ballon juste avant qu'Anne
ne le relâche. La force d'attraction de la Terre sur le ballon est de 4,4 N et Anne
exerce une force de 52 N pour maintenir le ballon vers le bas. L'eau exerce une force
de poussée sur le ballon. Cette force, appelée poussée d'Archimède, est celle qui
permet au ballon de flotter.

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.

snell's law

refractve index = sin incidence / sin refraction

b. false

explanation:

suppose a rock in free fall is dropped off a cliff. after falling for 5 seconds, its speed would not be 100 m/s.