It means that the momentum increases, decreases, or simply changes its direction. The latter is because momentum is a vector quantity (that is, the direction is relevant). Momentum is defined as the product of velocity and mass.
"Changes" can be a verb-- third person singular of "to change." Or it can be a plural noun. Change refers to doing something different; or an action that becomes different in some way. For example,...
Momentum is basically the amount of force it takes to slow something down. Force is Mass times Acceleration, so weight and speed are a factor. A large object like a bus, moving at even a slow speed...
Their are two different kinds of Change. One is change as in money and the other is one like you CHANGE from angry to sad. That was just an example for the angry to sad thing.But its just when you...