A projectile is launched from ground level at an angle of 30 degrees above the horizontal. Neglect air resistance and consider the motion from just after the moment it is launched to just before the moment it lands on the ground. When does the projectiles velocity equal its launch velocity?

At the highest point.
The projectile's velocity is never equal to its launch velocity after launch.
The projectile's velocity is always equal to its launch velocity.
Just before landing on the ground.
Halfway back to the ground.
Halfway to the highest point.

The projectile's velocity is never equal to its launch velocity after launch.

Explanation:

This is a tricky question, and the difference between the speed and the velocity should be clarified.

The velocity is a vector and the speed is a scalar quantity, which is basically the magnitude of velocity.

The projectile's initial velocity has a direction (30° above horizontal) and a magnitude. This magnitude is equal to its speed just before landing on the ground, however this is not equal to its velocity, because this time the direction is towards the ground. Therefore, the velocity of the projectile is never equal to its launch velocity.

answer: d. a cme increases the amount of energy in the solar wind

explanation:

coronal mass ejections, also called cmes, are large clouds of plasma and magnetic field that erupt from the sun. only when the cloud is aimed at earth will the cme hit earth and therefore cause impacts. high-speed solar wind streams come from areas on the sun known as coronal holes.

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.