AccelerationAcceleration

Acceleration

• The rate of change in velocity

Acceleration

• The rate of change in velocity

• Examples….– Speeding up

• Positive acceleration

– Slowing down• Negative acceleration• Deceleration

– Changing direction• Centripetal acceleration

Acceleration

• Compare to speed

• Acceleration is the rate of change in either speed or direction, while speed is the rate of change in position. They are both rates, but they are rates of different things.

Acceleration

• Formula for calculating acceleration:

t

vva

sf

time

locitystartingveityfinalveloconaccelerati

Acceleration

• Formula for calculating acceleration:

Vf = final velocity

Vs = starting velocity

t= time

a = acceleration

t

vva

sf

Acceleration

• One last way to write that formula:• Which is read delta v over t or change in

velocity over time.

ta

v

Acceleration: Example

• What is the average acceleration of a subway train that speeds up from 6 m/s to 12 m/s in 2s?

t

vva

sf

Acceleration: Example

• What is the average acceleration of a subway train that speeds up from 6 m/s to 12 m/s in 2s?

Vf = 12 m/s a = ?

Vs = 6 m/s

t= 2 s

Acceleration Problems What is the average acceleration of a subway train that speeds up from 6 m/s to 12 m/s in 2s?

vf = 12 m/s

vs = 6 m/s

t = 2s

ssms

sms

smsma

//32

/62

/6/12

Acceleration Problems

A person is traveling at 20 m/s in a car when the car hits a tree. The person comes to a complete stop in 0.4 seconds. What was the person’s acceleration?

Acceleration ProblemsA person is traveling at 20 m/s in a car when the car hits a tree. The person comes to a complete stop in 0.4 seconds. What was the person’s acceleration?

vs = 20 m/s

vf = 0 m/st = 0.4s

t

vva

sf

Acceleration ProblemsA person is traveling at 20 m/s in a car when the car hits a tree. The person comes to a complete stop in 0.4 seconds. What was the person’s acceleration?

vs = 20 m/s

vf = 0 m/st = 0.4s

ssms

sms

smsma

//504.0

/204.0

/20/0

Recognizing acceleration on a graph

This graph shows positive acceleration because the object is getting faster. The distance traveled in each second is increasing. The graph is becoming more steep.

Recognizing acceleration on a graph

This graph shows negative acceleration because the object is getting slower. The distance traveled each second is decreasing. The graph is getting less steep.

Dis

tan

ce(m

)

Time (s)