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What Is Acceleration?
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What Is Acceleration?

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What Is Acceleration?

Acceleration is a change in velocity.

An example of acceleration

1

This woman is moving at 3 m/s3 \space m/s, so this image tells us the woman's _____________.

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2

One second later the woman is moving at 7m/s7 m/s. What happened?

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3

In other words, the woman has "accelerated"

Over the course of 1 second, she sped up from 3 m/s3 \space m/s to 7 m/s7 \space m/s

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Which one of these do you think has the fastest acceleration?

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Speed and velocity describe how quickly an object travels. What best describes acceleration?

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How to recognise acceleration

1

What type of graph is this?

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2

This is a distance - time graph.

It tells you the position of an object at any point in time.

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3

What does the gradient of this D-T graph tell us?

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4

So the gradient or slope of a D-T graph shows us the velocity the object has. Is this particular object travelling at a constant velocity?

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5

So if the speed of this object is not constant, in 1 word what is it doing?

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6

So, acceleration is the change in speed or velocity of an object.

This means that a D-T graph with a changing gradient, or a curved line, represents an accelerating object.

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Acceleration and deceleration

1

What is this cyclist doing?

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2

Is this cyclist accelerating?

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3

The cyclist's acceleration is...

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4

So this cyclist has a negative acceleration.

This is the same as saying that this cyclist is decelerating.

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True or false: Accelerating at 3 m/s2-3 \space m/s^2 is the same as decelerating at 3 m/s23 \space m/s^2

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So acceleration can be either positive (speeding up) or negative (slowing down). Do you think you can also talk about both positive and negative deceleration?

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1

So an object getting slower and slower has a negative acceleration whereas an object getting faster and faster has a positive acceleration. What does that make acceleration?

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2

So, what is the best description of acceleration?

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Summary!

1

Acceleration is how fast the velocity of an object changes

Or its rate of change of velocity.

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2

Acceleration can be shown by a curved line on a D-T graph

This image is a good example of an object that is accelerating

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3

Acceleration can be both positive and negative

Positive values for acceleration means speeding up, for example 5 m/s25 \space m/s^2

Negative values for acceleration means slowing down, for example 5 m/s2-5 \space m/s^2

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4

You can also use the word "deceleration" for negative acceleration

For example, accelerating at 5 m/s2-5 \space m/s^2 is the same as decelerating at 5 m/s25 \space m/s^2

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5

You cannot have negative values for deceleration

Deceleration always means slowing down, so it doesn't make sense to have both negative and positive values for deceleration.

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