Answer:
A chair at rest on the floor has two forces acting on it its own weight that pulls it downward and the floor pushing upward on the chair, both of these forces are acting on it but the net force is 0, so the chair remains at rest and its velocity stays at 0.
Answer:
electrons
Explanation:
An electric current is said to exist when there is a net flow of electric charge through a region. In electric circuits this charge is often carried by electrons moving through a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in an ionized gas (plasma).
I think it’s the first option
Answer:
a) 
b)
º
c) 
Explanation:
From the exercise we know that the collision between Daniel and Rebecca is elastic which means they do not stick together
So, If we analyze the collision we got

To simplify the problem, lets name D for Daniel and R for Rebecca
a) 
Since Daniel's initial velocity is 0



Now, lets analyze the movement in the vertical direction

Since 


Now, we can find the magnitude of Daniel's velocity after de collision

b) To know whats the direction of Daniel's velocity we need to solve the arctan of the angle
º
c) The change in the total kinetic energy is:
ΔK=
ΔK=![\frac{1}{2}[(45kg)(8m/s)^2+(70kg)(7.32m/s)^2-(45kg)(14m/s)^2]=-1094.62J](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B2%7D%5B%2845kg%29%288m%2Fs%29%5E2%2B%2870kg%29%287.32m%2Fs%29%5E2-%2845kg%29%2814m%2Fs%29%5E2%5D%3D-1094.62J)
That means that the kinetic energy decreases