ACCELERATIONACCELERATION

Motion is change of positionMotion is described by velocity:

How fast? Which way?Changing motion means:

Speeding up,Slowing down,

Changing direction (turning)

ACCELERATIONACCELERATION• A car is accelerating whenever there is a change

in velocity• Acceleration also applies to changes in direction.

•It is important to distinguish between speed and velocity.

Acceleration is defined as the rate of change in velocity, rather than speed

ACCELERATIONACCELERATION

Acceleration is the rate at which velocity changes:Acceleration is how fast how fast changes or how fast the direction changes

Falling upward: Falling upward: constant accelerationconstant acceleration

Now consider a ball thrown straight up at 30 m/s: What happens on the way up?How fast is the ball moving 1 s, 2 s, 3 s later?Where is the ball when v = 0?How long does the ball take to reach the

highest point?How fast is the ball moving 4 s later?How long does the ball take to reach the

person? How fast is the ball moving when it reaches

the person?

Ball Toss ExperimentBall is in your hands

Ball is in your hands

Ball is in your hands

Ball is in your hands

Ball Toss Experiment

Ball is in your hands

Ball is in your hands

Ball is in Ball is in the airthe air

Ball is in Ball is in the airthe air

Motion with Constant AccelerationMotion with Constant Acceleration

equal

- 4.8 X 2 = 9.6equal

Motion with Constant AccelerationMotion with Constant AccelerationGeneral equations:

y = ½ at2 + vot

v = at + vo

a is constant ( a number)

Free Fall: Constant AccelerationThe acceleration of an object in free fall is about 10 meters per second every secondOr 10 m/s/sThe rock is falling faster and faster:Each second its velocity increases by 10 m/s

Time, seconds

Velocity, m/s

01234

t

Time, seconds

Velocity, m/s

0 01 102 203 304 40

t 10t

Fill out the table:

Graph these values: make a velocity-time graph

Motion with Constant AccelerationMotion with Constant Acceleration

Velocity-Time Graph

On a velocity-versus-time graph, On a velocity-versus-time graph, acceleration = slopeacceleration = slope

Free Fall: Constant AccelerationThe acceleration of an object in free fall is about 10 meters per second every secondOr 10 m/s/sThe rock is falling faster and faster:Each second its velocity increases by 10 m/s

Time, seconds

Velocity, m/s

0 01 102 203 304 40

t 10t

Motion with Constant AccelerationMotion with Constant Acceleration

Position-Time Graph

y = ½ aty = ½ at22

Position, Velocity, and Acceleration

Motion Graphs

Constant Acceleration Graphs

Race Cars