Acceleration

Acceleration:

1. the rate of change of velocity.

2. can occur through a change in speed or direction.

3. Two types of acceleration:

a. Positive Acceleration- -velocity and acceleration are in the same direction.

AccelerationVelocity

b. Negative Acceleration

-velocity & acceleration are in opposite directions.

-also called deceleration

Velocity Acceleration

Calculating Acceleration:

Acceleration =Velocity final – Velocity initial time

or

a = vf – vi

tif

if

tt

vv

t

va

Units of Acceleration

___meters____ second x second

or

m/s2

-If your answer is a positive number, this means the object is accelerating. (positive acceleration)

-If your answer is a negative number, this means the object is decelerating. (negative acceleration)

POSITIVE OR NEGATIVE?

Variations of the Acceleration Formula

Solving for time: t = vf – vi

a

Solving for final velocity: vf = at + vi

Solving for initial velocity: vi = vf

at

1. A driver floors the gas pedal on her Ferrari and reaches 35 m/s in about

4.3 seconds. Assuming the car started at rest, how fast did it accelerate?

a =vf =vi =t =

2. A bicyclist hits a moose while traveling at 19 m/s. It took the bicyclist .25 seconds to stop. Luckily the moose was fine, but the bicyclist

had to be transported to local. At what

what rate did the bicyclist decelerate?

a = vf =vi =t =

3. A water balloon dropped from a window accelerates at a speed of 9.8 m/s2

reaching a final velocity of 15 m/s before hitting a person. How much time does it take the balloon to reach this rate of acceleration?

a =Vf=Vi=t=

4. A swimmer speeds up from 1.6 m/s to 2.2 m/s during the last 20 seconds of his workout. What was his acceleration during this interval?

a =vf =

vi =t =

5. A rocket is launched from the white sands test site. It has a mass of 800 kg and can reach a top velocity of 700 m/s. If it takes 3.1 seconds to reach this velocity, what is its acceleration?

a=vf=vi=t=