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Free Response Questions (FRQs)

Unit 1 FRQ (Kinematics) Answers

3 min readβ€’december 22, 2021


AP Physics 1 🎑

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AP Physics 1 Free Response Question for Kinematics

πŸ‘‹ Welcome to theΒ AP Physics Unit 1 FRQ (Kinematics) Answers.Β Have your responses handy as you go through the rubrics to see how you did!
⏱ Remember, 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.)

Learning Objectives & Science Practices

  • 3.A.1.1 Express the motion of an object using narrative, mathematical, and graphical representations. [SP 1.5, 2.1, 2.2]
  • 4.A.2.1 Make predictions about the motion of a system based on the fact that acceleration is equal to the change in velocity per unit time, and velocity is equal to the change in position per unit time. [SP 6.4]
  • 4.A.2.3 Create mathematical models and analyze graphical relationships for acceleration, velocity, and position of the center of mass of a system and use them to calculate properties of the motion of the center of mass of a system. [SP 1.4, 2.2]

Reference Video


Setup

A student of mass m stands on a platform scale in an elevator in a tall building. The positive direction for all vector quantities is upward. The vertical position of an elevator as a function of time is shown below. The velocity at 6 seconds is -30 m/s.
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-OwbAt6whMSaZ.png?alt=media&token=bb3badee-526e-4b40-b55c-72a121ac7f4c

Questions with Answers & Rubric

(a) On the grid below, plot the velocity of the elevator as a function of time. (3pts)

https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-d3BCmD6cfdYK.png?alt=media&token=b2f16975-4ca2-4dad-b5da-f9c0bedd226d
  • 1pt: For a horizontal line at 20 m/s from t=0 to t=2
  • 1pt: For a straight line starting at 20 m/s at t=2, and ending at 0 m/s at t=4
  • 1pt: For a straight line starting at 0 m/s at t=4, and ending at -30 m/s at t=6
πŸ“„ Additional Resources

Resources:

(b) Calculate the average acceleration for the time period t = 2s to t = 4s. (3pts)

  • 1pt: For a description or equation for acceleration either as the slope of the v vs. t graph, or a = βˆ†v / βˆ†t
  • 1pt: For the work to determine the acceleration, a = (0-20) / (4-2)
  • 1pt: For the correct answer with units, a = -10 m/s^2
πŸ“„ Additional Resources

An inspector provides the student with the following graph showing the acceleration a of the elevator as a function of time t.
https://firebasestorage.googleapis.com/v0/b/fiveable-92889.appspot.com/o/images%2F-89NNii2BJxNF.png?alt=media&token=764bb825-b50f-424b-b28b-b86ffdd22218

Resources:

(c) During what time interval(s) is the speed of the elevator constant? How do you know? (3pts)

  • 1pt: For the time interval of 10-13 sec
  • 1pt: For the time interval of 19-20 sec
  • 1pt: For a correct explanation that for a constant velocity, the acceleration of the system must be equal to 0
πŸ“„ Additional Resources

Resources:

Next Steps

  • 🧠 Want to continue reinforcing your knowledge of Unit 1? Check out Unit 1 Trivia, either as a document or as a game.
  • ⏭ Ready to move on to the next topic? Take a look at the collection of Unit 2 resources.
  • πŸ“š Want to review multiple units? Check out all of the AP Physics FRQs.
  • 🀝 Got more questions? Want to help others studying the same topic? Jump into a room inΒ Hours!

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πŸ‘‰AP Physics Essentials
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