AccelerationAccelerationMovie GalileoMovie Galileo

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GalileoGalileo

1600’s 1600’s Studied how things Studied how things

fellfell Didn’t have a good Didn’t have a good

clockclock Rolled balls down an Rolled balls down an

inclined planeinclined plane Found that the speed Found that the speed

increased as it rolled increased as it rolled down the rampdown the ramp

GalileoGalileo

t = 0t = 1 second

t = 2 seconds

t = 3 seconds

AccelerationAcceleration

Acceleration is the rate at which Acceleration is the rate at which velocity (speed or direction) velocity (speed or direction) changes.changes.

Rate = time Rate = time

So,So, acceleration is change in velocity per time.acceleration is change in velocity per time.

3 Types of acceleration3 Types of acceleration

1.Increasing Speed

2.Decreasing speed

3.Changing DirectionBecause of velocity

A= A= change in velocitychange in velocity

timetime

Change in velocity = final Change in velocity = final – – starting starting

velocity velocity velocity velocity

A= A= FV - IVFV - IV

timetime

Calculating Acceleration

Acceleration =Velocity(final) - Velocity(original)

time

A car traveling at 60 mph accelerates to90 mph in 3 seconds. What is thecar’s acceleration?

Acceleration =Velocity(final) - Velocity(original)

time

A car traveling at 60 mph accelerates to90 mph in 3 seconds. What is thecar’s acceleration?

=90 mph - 60 mph

3 seconds

=30 mph

3 seconds

= 10 mph/second

Acceleration =Velocity(final) - Velocity(original)

time

A car traveling at 60 mph accelerates to90 mph in 3 seconds. What is thecar’s acceleration?

Acceleration =Velocity(final) - Velocity(original)

time

A car traveling at 60 mph slams on the breaks to avoid hitting a deer. The car comes to a safe stop 6 seconds after applying the breaks. What is thecar’s acceleration?

=0 mph - 60 mph

6 seconds

=- 60 mph

6 seconds

= - 10 miles per hour per second

A car at rest can go 90 A car at rest can go 90 km/h in 9 seconds. What is km/h in 9 seconds. What is

the acceleration?the acceleration?

A person was running A person was running down a ramp. They started down a ramp. They started going 4 m/s down and then going 4 m/s down and then ended up going 22 m/s at ended up going 22 m/s at the bottom. What was the the bottom. What was the persons acceleration down persons acceleration down

the ramp.the ramp.

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PositivePositive acceleration acceleration

Negative Negative accelerationacceleration

- A constant - A constant acceleration acceleration

produces a straight produces a straight line or linear slope line or linear slope

(rise/run). (rise/run).

- The slope of a non-- The slope of a non-linear velocity-time linear velocity-time graph (rise/run) will graph (rise/run) will predict an objects predict an objects

instantaneous instantaneous acceleration. acceleration.

a = v/ta = v/t

GalileoGalileo

Back to GalileoBack to Galileo When things fall they get faster and When things fall they get faster and

faster.faster.

Free fallFree fall The constant acceleration of The constant acceleration of

an object moving only under an object moving only under the force of gravity is "g". the force of gravity is "g".

The acceleration caused by The acceleration caused by gravity is 10 m/sgravity is 10 m/s22

If there was no air, all If there was no air, all objects would fall at the objects would fall at the same speedsame speed

Doesn’t depend on massDoesn’t depend on mass After 1 second falling at 10 After 1 second falling at 10

m/sm/s After 2 seconds 20 m/sAfter 2 seconds 20 m/s 3 seconds 30 m/s3 seconds 30 m/s

FallingFalling Air resistance will Air resistance will

increase as it falls increase as it falls fasterfaster

An upward force on An upward force on the objectthe object

Eventually gravity Eventually gravity will balance with air will balance with air resistanceresistance

Reaches terminal Reaches terminal velocity - highest velocity - highest speed reached by a speed reached by a falling object.falling object.

Terminal velocityTerminal velocity Force of gravity is Force of gravity is

constantconstant air resistance increases as you speed up until the force is equal

Equal forces, no acceleration constant velocity terminal velocity