## Alphabetical

# acceleration

*[noun] *

The change in an object's velocity over time, measured in distance per unit time per unit time (for example meters per second per second or m/s^{2}). Compare to velocity. Acceleration (a) is calculated by dividing the change (symbolized by Δ, the Greek letter delta) in velocity (v) by the change in time (t):

a = Δv/ Δt.

This can also be written as:

a = v_{2}-v_{1}/ t_{2}-t_{1}, where v_{1} and t_{1} denote the starting velocity and time and v_{2} and t_{2} denote the ending velocity and time.

To illustrate, imagine a car speeding up (accelerating) from a stand still (0 meters/second) to a speed of 15 meters/seconds over the course of 5 seconds. The car's total increase in velocity is 15 meters/second. During each of the 5 seconds that the car is accelerating, its velocity increases by 3 meters/second until it reaches its top speed. (After one second the car is traveling at a velocity of 3 meters/second; after 2 seconds, it's traveling at a velocity of 6 meters/second, and so on). Therefore, the car's rate of acceleration is 3 meters per second per second or 3 m/s^{2}. Using the equation above:

a = v_{2}-v_{1}/ t_{2}-t_{1}

a = 15-0 / 5-0

a = 15/5

a = 3 m/s^{2}

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