Unit 1 FRQ (Kinematics) Answers

AP Physics 1 Free Response Question for Kinematics

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

Questions with Answers & Rubric

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

• 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

• Replay: Velocity vs. Time Graphs

(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 = ∆v / ∆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

• Study Guide: Position, Velocity, and Acceleration

(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

• Replay: Acceleration

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.

• 📚 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 in Hours!