According to the kinetic molecular theory, the pressure of a gas in a container will increase if the number of collisions with the container wall increases.
<u>Explanation:</u>
Keeping the volume of the vessel constant, if we increase the amount of gas in it; the pressure will increase.
This is because when the number of gas particles increases in that limited volume, they hit the walls of the container with more energy and hence, the overall pressure of the gas increases.
If we decrease the amount of gas in the vessel or increase the volume for the same amount of gas, the pressure decreases. As the pressure inside the vessel depends upon the gas supplied in the container.
Gravity is all ways pulling down and the normal force acting on top of the object and for it to have to push or pull to the object
Acceleration= change in velocity/time
Well the trivial answer is zero, since there is indeed a "zero vector". Assuming you aren't allowed to use the zero vector you would need at least two. They would be antiparallel and of equal magnitude. (That is be pointing in opposite directions and have the same length)