Acceleration and Momentum   Acceleration — Rate of change of velocity (speed and specific direction) over time. Positive Acceleration- speed increases Negative Acceleration- speed decreases

Average acceleration Formula: a = vf – vi Where: t a = accerlation (m/s2) vf = velocity final (m/s) vi = velocity initial (m/s) t = time (s) We shorten it as: a = v t Calculating Acceleration Change in velocity is Vf-Vi or V • Answers will look like: m/s2 - "meters per second squared"

Acceleration can be graphed with velocity on the y-axis and time on the x-axis. An object that is decelerating (-)on a velocity-time graph line that slopes down. An object that is accelerating(+) on a velocity time graph  line that slopes upward. A horizontal line would indicate no acceleration or zero speed.

Momentum The amount of matter in an object  Mass Interia tendency of an object to resist a change in motion. Momentum —how hard it is to stop an object

p = m x v P m v p = momentum (kg •m/s) m = mass (kg) Formula for Momentum p = momentum (kg •m/s) m = mass (kg) v = velocity (m/s) p = m x v P m v

Momentum increases if the mass or velocity of the object increases. Momentum has direction that is the same as its velocity

Law of Conservation of Momentum —the total momentum of objects that collide with each other does not change. It only occurs when other outside forces act on the object.

There are two ways collisions can occur. Objects stick & move still stuck together, although possibly at different speeds (inelastic collision)

Two objects bounce off each other when they collide, & transfer momentum from one to the other (elastic collision)

In both cases, the total momentum of the objects that collide is the same before and after the collision