Unit 5 FRQ (Momentum)

AP Physics 1 Free Response Question on Momentum

👋 Welcome to the AP Physics 1 Unit 5 FRQ (Momentum). These are longer questions, so grab some paper and a pencil, or open up a blank page on your computer. After you finish, you can see how you did with Unit 5 FRQ (Momentum) Answers.

⏱ The AP Physics 1 exam has 5 free-response questions, and you will be given 90 minutes to complete the FRQ section. (This means you should give yourself ~18 minutes to go through each practice FRQ.)

• 🤔 Need a quick refresher of the unit as a whole? Check out the Unit 5 Overview (Coming soon!)
• • 😩 Getting stumped halfway through answering? Look through all of the available Unit 5 Resources.

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Setup

Identical Blocks 1 and 2 are placed on a horizontal surface at points A and E, respectively, as shown. The surface is frictionless except for the region between points B and C, where the surface is rough. Beginning at time tA, Block 1 is pushed with a constant horizontal force from Point A to Point B by a mechanical plunger.

Upon reaching Point B, Block 1 loses contact with the plunger and continues moving to the right along the horizontal surface toward Block 2. Block 1 collides with and sticks to Block 2 at Point E, after which the two-block system continues moving across the surface, eventually passing Point F.

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Questions

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Part A

(i) On the axes below, sketch the speed of the center of mass of the two-block system as a function of time, from time tA until the blocks pass Point F at time tF. The times at which Block 1 reaches Points A through F are indicated on the time axis.

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Part B

The system is reset and Block 1 is again released. The following conditions now exist:

In addition, there is no friction on the horizontal surface except for between letters B and C.

(i) Determine the speed of Block 1 at Point B.

(ii) Determine the speed of Block 1 at Point D.

(iii) Determine the speed of the combined Blocks 1 and 2 at Point F.

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Part C

(i) Was momentum and/or energy conserved from Point D to Point F? Briefly explain your reasoning for EACH.

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Answers & Rubric

💯 Ready to see how you did? Take a look at the Unit 5 FRQ (Momentum) Answers.

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