Suppose you find yourself teetering on the edge of a cliff or the roof of a tall building with a heavy physics book in your hand. as you are about to fall, you suddenly remember how physics can save you! what law did you remember?

Law of Conservation of Momentum

Explanation:

According of Law of Conservation of Momentum:

"If the result of the forces acting on a body or system is null, its linear momentum remains constant in time ".

In fact, this law is actually a direct consequence of Newton's third law of motion:

"When two bodies interact between them, appear equal forces and opposite directions in each of them."  

To understand it better:  

Each time a body or object exerts a force on a second body or object, it (the second body) will exert a force of equal magnitude and direction but in the opposite direction on the first.

So, if you If you throw the heavy physics book forward, you will have a backward momentum (with the same magnitude and opposite direction), hence a backward force that will make you fall to the side of the building and you will not fall over the edge.

a displacement distance is size of displ

a lot of it means it can be "burned" for energy and sold at one price. if it is scarce, the price will go up