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Unit 2Lesson 2

Motion and Force

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Lesson 2 Key Question

Example: Consider giving a low-friction cart a quick shove along a track.

When an object is moving, does this mean there must be a force pushing it in the direction of its motion?

PART 1

Giving Cart a Quick Shove

After your shove, as it moves along the track, is there still a force pushing the cart forward?

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CQ 2-1: In the discussion between three students about the force acting on the cart after the quick

push, whom do you agree with?

A. SamanthaB. VictorC. AmaraD. None of them

PART 1

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Force and motion simulator

PART 2

• Highlight the sections of the graph where the hand was pushing the cart forward.

• Between your marked sections do you think there was still a force pushing the cart forward? Why do you think so?

Look at the simulator speed-time graph of a cart being given some quick pushes as it moves along a track.

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CQ 2-2: Which force-time graph best represents your thinking about the force pushing the cart forward as it

moves along the track?

A. Graph AB. Graph BC. Graph C

PART 2

A B C

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What does the simulator show?

PART 2

Watch a movie of the simulator being run.

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What does the simulator show?

PART 2

Which of the force-time graphs in CQ 2-2 looks most like the simulator result?

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Force and motion• During the periods when the

simulator cart was being given a shove, was there a force pushing it forward?

• What action in the real world do these simulator shoves correspond to?

• During the periods in between the simulated shoves was there a force pushing the cart forward?

PART 3

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Summarizing Questions• While the simulator cart was moving along the track,

was there a force pushing the simulator cart forward the whole time or only at certain times?

• During a contact push/pull interaction, what do you think is transferred from the source to the receiver: energy, force, both, or neither?

• During the periods while the cart was being given a shove, its speed increased. In between these periods its speed remained constant. Why do you think the speed behaved differently during these periods?

Summarizing Questions

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CQ 2-3: Suppose the force-time graph for a simulator cart looked like this. Which of the speed-time graphs below could be produced by applying a single force in this way?

A. Graph AB. Graph BC. Graph C

A B C

Summarizing Questions

Unit 2 Lesson 2 Homework

Learn how force and energy analyses are related

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