AccelerationSection 6.1 in your textbook.

Thinking questions

• Describe the physical sensations (feelings) that you have when you experience these changes in motion:

• Airplane taking off

• Car slowing down at a red light

• Driving along a circular ramp

• Why do you think that you feel these things?

Acceleration

• Symbol:

• Vector quantity (has direction)

• Describes a change in velocity during a specific time interval

• Verb: accelerate

Acceleration = change in velocity

• Object moves faster increase in magnitude (size) of velocity

• Object moves slower decrease in magnitude of velocity

• Object changes direction

What causes acceleration?

• Forces

• Anything that is pushing or pulling on the object

• No forces acting = no change in motion

Graphing Acceleration

• Acceleration is shown as a curve on a Position vs. Time graph

• The curve shows that velocity is changing

• The object has a larger change in position for each time interval

Acceleration on a Position vs. Time graph

Describe the motion for each graph.

Acceleration on a Position vs. Time graph

Increasing velocity in the positive direction

Increasing velocity in the negative direction

Decreasing velocity in the negative direction

Decreasing velocity in the positive direction

Acceleration on a Velocity vs. Time graph

• For each time interval, the object has a larger velocity, so it is accelerating

• Acceleration is the slope of a velocity vs. time graph

• Straight, increasing or decreasing line means constant acceleration

These 3 graphs all show velocity that is increasing and acceleration that is constant.

Zero Acceleration• Object is not

changing velocity

• Position-Time graph: straight line increasing or decreasing

• Velocity-Time graph: flat line

Direction of Acceleration

• Slope of a Velocity vs. Time graph gives us information about the direction of acceleration

• Positive acceleration: slope of a VT graph is +

• Negative acceleration: slope of a VT graph is -

Positive Acceleration*does not always mean

speeding up

What happens right here?

Negative acceleration*does not always mean

slowing downWhat happens right here?

What other information comes from a Velocity-Time

graph?

• Displacement!

• Find the area under a Velocity vs. Time graph

• Area of a rectangle = length x width

• Area of a triangle = ½ base x height

Why does finding the area give us displacement?

• Think about the quantities represented by “length”, “width”, “base” & “height” on a VT graph.

• If velocity is constant, the area is a rectangle multiply time x velocity

• If velocity is changing uniformly, the area is a triangle multiply time x velocity & divide by 2

• position changed a lot at the beginning, but a little at the end, so you’re actually finding the average change in position between the initial velocity & the final velocity

Find displacement over 5 seconds

Find displacement over 5 seconds

Homework

• Page 247: Section 6.1 Review

• Do questions #1-4 & #6-12 in your notebooks

• Next class I will check that you started

Next Class

• Come prepared to work with your group on the Scavenger Hunt Game

• I will be watching and listening to make sure that you are speaking English and working together