Acceleration

Definition Acceleration: rate at which velocity changes Remember: velocity is speed AND direction THREE ways that something can have acceleration: Increasing speed Decreasing speed Change in direction

Increasing Speed A softball accelerates when a pitcher throws it A car accelerates to pass another car on the highway You accelerate when you ride your bike down a hill

Decreasing Speed AKA: “negative acceleration” A softball decelerates when it lands in a glove A car decelerates when it stops at a red light

Change in Direction If an object is at a constant speed, but changing direction, it is accelerating A Ferris Wheel accelerates because it’s changing direction, but at a constant speed A car changes direction when rounding a curve.

Calculating Acceleration Acceleration = Final velocity – Initial velocity The SI unit of acceleration is m/s2 Time

Sample Problem As a roller coaster car starts down a slope, its speed is 4 m/s. But 3 seconds later, at the bottom, its speed is 22 m/s. What is its average acceleration? Initial Velocity: Vi Final Velocity: Vf Time:

Graphing Acceleration Speed vs. Time Graph