What type of relationship exists between momentum and mass

Momentum is directly proportional to an object's mass

Explanation:

See the attached picture.

The formula for momentum is P (momentum) = Mass x Velocity

So if mass increases, momentum increases.

Definitions just in case:

There is a direct proportion between two values when one is a multiple of the other (example: hourly pay, the more you work, the more money you make).  Inverse proportion occurs when one value increases and the other decreases (example: the more you work, the less work left to do)

trig 15.3 cos