if the elevator is moving upward with the constant speed the spring scale will read 18 N which is the mass of each of the two blocks attached by separate springs to the scale at opposite ends.
The total momentum of the universe is always the same and is equal to zero. The total momentum of an isolated system never changes. Momentum can be transferred from one body to another.
Momentum quantifies how likely an object is to stay in motion. Momentum can also be explained using the equation, p=mv, where p is equal to momentum, m is equal to mass, and v is equal to velocity.
