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Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be...

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Page 1: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.
Page 2: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Acceleration

Acceleration = speeding up

Acceleration – the rate at which velocity changes Can be an:

Increase in speed Decrease in speed Change in direction

Page 3: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Types of acceleration

Increasing speed Example: Car speeds up at green light

Decreasing speed Example: Car slows down at stop light

Changing Direction Example: Car takes turn (can be at

constant speed)

screeeeech

Page 4: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Question

How can a car be accelerating if its speed is a constant 65 km/h?

If it is changing directions it is accelerating

Page 5: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Calculating Acceleration

If an object is moving in a straight line

Time

SpeedInitialspeedFinalonAccelerati

__

Units of acceleration:Distance/ time = distance/time2

timem/s2

Page 6: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Calculating Acceleration

0 s 1 s 2 s 3 s 4 s

0 m/s 4 m/s 8 m/s 12 m/s 16 m/s

2/4

4

/0/16

__

sm

s

smsmTime

SpeedInitialSpeedFinalonAccelerati

Page 7: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Question

A skydiver accelerates from 20 m/s to 40 m/s in 2 seconds. What is the skydiver’s average acceleration?

2/10

2

/20

2

/20/40

__

sm

s

sm

s

smsmTime

speedInitialspeedFinalAccel

Page 8: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Graphing Acceleration

Can use 2 kinds of graphs Speed vs. time Position vs. time

Page 9: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Graphing Acceleration:Speed vs. Time Graphs

1)Speed is increasing with time = accelerating2)Line is straight = acceleration is constant

Page 10: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Graphing Acceleration:Speed vs. Time Graphs

1)In Speed vs. Time graphs:Acceleration = Rise/Run = 4 m/s ÷ 2 s = 2 m/s2

Run = 2 s

Rise = 4 m/s

Page 11: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Graphing Acceleration:Position vs. Time Graphs

1)On Position vs. Time graphs a curved line means the object is accelerating.

2)Curved line also means your speed is increasing. Remember slope = speed.

Page 12: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Question

Above is a graph showing the speed of a car over time.1) How is the speed of the car changing (speeding up,

Slowing down, or staying the same)?2) What is this car’s acceleration?

1) The car is slowing down2) Acceleration = rise/run = -6m/s ÷3s = -2 m/s2

Run = 3 s

Rise = -6 m/s

Page 13: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Question:

1)Which line represents an object that is accelerating?

The black and red lines represent a objects that are accelerating. Black is going a greater distance each second, so it must be speeding up. Red is going less each second, so must be slowing down

Remember: in position vs. time graphs: curved line = accelerating,

straight line = constant speed

Page 14: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Question: Hard one

Page 15: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Free fall

The constant acceleration of an object moving only under the force of gravity

If there was no air, all objects would fall at the same speed regardless of the masses

Page 16: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Acceleration due to gravitational force

d = vit + ½gt2

If vi = 0, then d = ½ gt2

g = acceleration due to the force of gravity

= 9.8 m/s2

= 10 m/s2

Page 17: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Free fall

After 1 second falling: v= 10 m/s

After 2 seconds: v = 20 m/s

After 3 seconds: v = 30 m/s

Page 18: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Falling Air resistance will

increase as it falls faster

An upward force on the object

Eventually gravity will balance with air resistance

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

Page 19: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Bozeman videos

http://www.bozemanscience.com/position-vs-time-graph-part-2

http://www.bozemanscience.com/speed-velocity-acceleration

Page 20: Acceleration Acceleration = speeding up Acceleration – the rate at which velocity changes Can be an: Increase in speed Decrease in speed Change in direction.

Questions

Answer the following questions and email me your answers. ([email protected] )

1. How can a car accelerate without the speedometer changing?

2. What does the slope of a velocity vs time graph give you?

3. What is the value of the acceleration due to the force of gravity on Earth?

4. What is the color of the object that is rolled across the table by Mr. Andersen?


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