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 This means that to achieve the *same momentum*, a smaller force can be applied for a longer period of time or a larger force can be applied in a smaller period of time.
 
+As momentum is a **vector**, it must have a direction, and these differences in direction and therefore sign must be taken under consideration.
+
+!!! example
+    Bouncing balls change direction, so one of the velocities is in a direction opposite of the other.
+
 ### Impulse
 
 Impulse is the change in momentum of an object because of a force. It is expressed mathematically as $\vec{J}$, and is also represented in Newton seconds.