Barack is playing basketball in his back yard. He takes a shot 7.0 m from the basket (measured along the ground), shooting at an
angle of 45 degrees. The ball is 2.0 m off the ground when it leaves his hand, and hits the backboard 3.5 m off the ground. Neglecting air friction, about how long is the ball in flight?
Force per area is pressure so I think the answer would be air pressure. Relative pressure sounds like it is a measure of pressure relative to something else.
The atomic mass. By taking two different types of the same element and calculating the average based on the amount of each type in the world, you get the basic atomic difference.