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AP Physics 1 Unit 7 practice questions

Try 10 multiple-choice questions from Unit 7 here. Pick an answer to see why it's right or wrong, then take the timed test above for a full AP-style set.

  1. Question 1

    A block of mass mm attached to a spring with spring constant kk oscillates with period TT. If the mass is replaced by a block of mass 9m9m and the spring is replaced by one with spring constant 4k4k, which expression represents the new period of the system?

    0.67T0.67 T

    1.5T1.5 T

    2.25T2.25 T

    3.0T3.0 T

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    Answer: (B)

    Period TT is proportional to m/k\sqrt{m/k}. The factor of change is 9/4=3/2=1.5\sqrt{9/4} = 3/2 = 1.5. The new period is 1.5T1.5T.

  2. Question 2

    A simple pendulum of length LL has a period TT on Earth. If the pendulum is moved to a planet where the gravitational acceleration is 4g4g, which expression represents the new period of the pendulum?

    0.25T0.25 T

    0.50T0.50 T

    2.0T2.0 T

    4.0T4.0 T

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    Answer: (B)

    Period is inversely proportional to the square root of gravity (T∝1/gT \propto 1/\sqrt{g}). The factor is 1/4=0.51/\sqrt{4} = 0.5. The new period is 0.5T0.5T.

  3. Question 3

    A block of mass mm is attached to two identical springs with spring constant kk. In System 1, the springs are arranged in parallel. In System 2, the springs are arranged in series. How do the effective spring constant and the period of oscillation compare between System 1 and System 2?

    System 1 has a larger spring constant and a shorter period

    System 1 has a larger spring constant and a longer period

    System 1 has a smaller spring constant and a shorter period

    System 1 has a smaller spring constant and a longer period

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    Answer: (A)

    Parallel springs add constants (keff=2kk_{eff} = 2k), while series springs add reciprocals (keff=k/2k_{eff} = k/2). Since period T=2πm/keffT = 2\pi\sqrt{m/k_{eff}}, a larger keffk_{eff} in System 1 results in a shorter period.

  4. Question 4

    An object of mass mm attached to an ideal spring with spring constant kk oscillates with a period TT. If the spring is replaced by one with constant 4k4k and the object is replaced by one with mass m/4m/4, what is the new period of oscillation?

    T/16T/16

    T/4T/4

    TT

    4T4T

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    Answer: (B)

    Using T=2πmkT = 2\pi\sqrt{\frac{m}{k}}, the factor of change is 1/44=116=14\sqrt{\frac{1/4}{4}} = \sqrt{\frac{1}{16}} = \frac{1}{4}.

  5. Question 5

    A block of mass mm is attached to a vertical spring with spring constant kk. When the block is at its equilibrium position, the spring is stretched by a distance dd from its natural length. Which of the following expressions gives the period TT of oscillation for this system in terms of dd and the acceleration due to gravity gg?

    2πdg2\pi\sqrt{\frac{d}{g}}

    2πgd2\pi\sqrt{\frac{g}{d}}

    12πdg\frac{1}{2\pi}\sqrt{\frac{d}{g}}

    12πgd\frac{1}{2\pi}\sqrt{\frac{g}{d}}

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    Answer: (A)

    At equilibrium, the spring force balances the weight (kd=mgkd = mg), so the ratio m/km/k equals d/gd/g. Substituting this into the standard period equation T=2πm/kT = 2\pi\sqrt{m/k} yields T=2πd/gT = 2\pi\sqrt{d/g}.

  6. Question 6

    A particle of mass mm undergoes simple harmonic motion with amplitude AA attached to a spring of spring constant kk. Which of the following expressions correctly gives the maximum speed vmaxv_{max} of the particle?

    AkmA\sqrt{\frac{k}{m}}

    AmkA\sqrt{\frac{m}{k}}

    A2kmA^2\sqrt{\frac{k}{m}}

    A2mkA^2\sqrt{\frac{m}{k}}

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    Answer: (A)

    Conservation of energy equates the maximum potential energy (12kA2\frac{1}{2}kA^2) to the maximum kinetic energy (12mvmax2\frac{1}{2}mv_{max}^2). Solving for vmaxv_{max} yields Ak/mA\sqrt{k/m}.

  7. Question 7

    A simple pendulum of length LL and mass mm is displaced by a small angle θ\theta from the vertical. Which of the following expressions gives the magnitude of the restoring force FrestoringF_{restoring} acting on the mass along its arc of motion?

    mgsin⁡θmg\sin\theta

    mgcos⁡θmg\cos\theta

    mgtan⁡θmg\tan\theta

    mg(1−cos⁡θ)mg(1-\cos\theta)

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    Answer: (A)

    The restoring force is the component of gravity acting tangent to the arc of motion. Resolving the weight vector mgmg yields a tangential component of mgsin⁡θmg\sin\theta directed toward equilibrium.

  8. Question 8

    A block of mass mm oscillates on a frictionless horizontal surface attached to a spring with spring constant kk. If the amplitude of oscillation is AA, which expression gives the magnitude of the maximum acceleration amaxa_{max} of the block?

    kAm\frac{kA}{m}

    mAk\frac{mA}{k}

    kmA\frac{km}{A}

    kmA\frac{k}{mA}

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    Answer: (A)

    According to Newton's second law (F=maF=ma), the maximum force occurs at maximum displacement (Fmax=kAF_{max} = kA). Solving for acceleration gives amax=kA/ma_{max} = kA/m.

  9. Question 9

    A simple pendulum of length LL is suspended from the ceiling of an elevator that is accelerating upward with a constant acceleration aa. Which of the following expressions gives the period TT of the pendulum in this reference frame?

    2πLg+a2\pi\sqrt{\frac{L}{g+a}}

    2πLg−a2\pi\sqrt{\frac{L}{g-a}}

    2πLa2\pi\sqrt{\frac{L}{a}}

    2πLg2\pi\sqrt{\frac{L}{g}}

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    Answer: (A)

    The effective gravitational field in the accelerating frame is geff=g+ag_{eff} = g + a. Substituting this into the standard pendulum period formula yields T=2πL/(g+a)T = 2\pi\sqrt{L/(g+a)}.

  10. Question 10

    An object of mass mm oscillates on a spring with a period TT. Which of the following expressions correctly represents the spring constant kk in terms of mm and TT?

    4π2mT2\frac{4\pi^2 m}{T^2}

    2πmT2\frac{2\pi m}{T^2}

    m4π2T2\frac{m}{4\pi^2 T^2}

    4π2T2m\frac{4\pi^2 T^2}{m}

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    Answer: (A)

    Starting with the period formula T=2πm/kT = 2\pi\sqrt{m/k}, squaring both sides gives T2=4π2m/kT^2 = 4\pi^2 m/k. Rearranging to solve for kk yields k=4π2m/T2k = 4\pi^2 m/T^2.

What's on the AP Physics 1 Unit 7 practice test

The standard version takes about 88 minutes and follows the timing and directions of the AP exam, sized to one unit:

  • 20 Multiple Choice Questions (40 minutes)
  • 1 FRQ – FRQ 1 – Mathematical Routines (24 minutes)
  • 1 FRQ – FRQ 2 – Translation Between Representations (24 minutes)

Questions are drawn from 645 multiple-choice questions and 44 FRQs written for Unit 7, Oscillations.

Practice AP Physics 1 Unit 7 FRQs

Answer the unit's free-response questions one at a time and get a score on every part.

Review Unit 7 before you start

Other AP Physics 1 unit tests