5 Steps to a 5: AP Physics 1: Algebra-Based 2017 (2016)

STEP 2

Determine Your Test Readiness

CHAPTER 4   Test Yourself: AP Physics 1 Fundamentals

CHAPTER 5   Test Yourself: AP Physics 1 Question Types

CHAPTER 4

Test Yourself: AP Physics 1 Fundamentals

IN THIS CHAPTER

Summary: This chapter contains a short test designed to help you determine your strengths and weaknesses regarding the content and skills tested on the AP Physics 1, Algebra-Based Exam.

Key Ideas

   Find out what you know—and don’t know—about mechanics, electricity, and waves. This will tell you how well you’re prepared for the subjects tested on the AP Physics 1, Algebra-Based Exam.

   From this self-assessment you can identify strengths and weaknesses and develop a personalized test-prep plan (see Chapter 3 ).

Self-Assessment: AP Physics 1 Fundamentals

Note that the questions in this self-assessment are not written in the style of the actual questions on the AP Physics 1, Algebra-Based Exam. The questions are designed to quickly determine your strengths and weaknesses, not to mimic actual test questions. In the next chapter you’ll encounter the different question types found on the actual AP Physics 1 Exam.

Answer the questions below. The correct answers with explanations are found at the end of this chapter. From this self-assessment you should get a sense of what your weaknesses are and be able to prioritize what areas you need to give the most attention. This self-assessment should be the basis for a test-prep plan that you develop for yourself (see Chapter 3 ).

Mechanics

1 .    What is the mass of a block with weight 100 N?

2 .    Give the equations for two types of potential energy, identifying each.

3 .    When an object of mass m is on an incline of angle θ , one must break the weight of the object into components parallel and perpendicular to the incline.

(a)   What is the component of the weight parallel to the incline?

(b)   What is the component of the weight perpendicular to the incline?

4 .    Write two expressions for work, including the definition of work and the work-energy principle.

5 .    Name several things that can never go on a free-body diagram.

6 .    Write two expressions for impulse. What are the units of impulse?

7 .    In what kind of collision is momentum conserved? In what kind of collision is kinetic energy conserved?

8 .    What is the mass of a block with weight W ?

9 .    A ball is thrown straight up. At the peak of its flight, what is the ball’s acceleration? Be sure to give both magnitude and direction.

10 .    A mass experiences a force with components 30 N to the right, 40 N down. Explain how to determine the magnitude and direction (angle) of the force.

11 .    Write the definition of the coefficient of kinetic friction, μ k . What are the units of μ k ?

12 .    How do you find acceleration from a velocity-time graph?

13 .    How do you find displacement from a velocity-time graph?

14 .    How do you find velocity from a position-time graph?

15 .    A cart on a straight track has a positive acceleration. Explain BRIEFLY how to determine whether the cart is speeding up, slowing down, or moving at constant speed.

16 .    Given the velocity of an object, how do you tell in which direction that object is moving?

17 .    When is the gravitational force on an object mg ? When is the gravitational force Gm 1 m 2 /r 2 ?

18 .    What is the direction of the net force on an object that moves in a circle at constant speed?

19 .    Under what conditions is the equation  valid? Give a specific situation in which this equation might seem to be valid, but is not .

20 .    Under what conditions is angular momentum conserved?

21 .    What is rotational inertia, and how is it calculated?

Electricity

22 .    What is the equation for the force of one charge on another?

23 .    What property of series resistors is the same for each and equal to the total?

24 .    What property of series resistors is different for each, adding to the total?

25 .    What property of parallel resistors is the same for each and equal to the total?

26 .    What property of parallel resistors is different for each, adding to the total?

27 .    The brightness of a bulb depends on what physical quantity?

Waves

Questions 28 and 29 relate to the preceding diagram of a standing wave.

28 .    On the diagram, label one wavelength.

29 .    The diagram represents particle displacement for a longitudinal wave in a pipe. Is this a pipe closed at one end, or a pipe open at both ends?

30 .    How are period and frequency related?

31 .    The Doppler effect affects which property of a wave?

32 .    A guitar string is tightened. What variable in v = λf is not affected?

Solutions for the AP Physics 1 Fundamentals Self-Assessment

Mechanics

1 .    Weight is mg . So, mass is weight divided by g , which would be 100 N/(10 N/kg) = 10 kg.

2 .    PE = mgh , gravitational potential energy;

PE = ½kx 2 , potential energy of a spring.

3 .    (a)   It is mg sin θ is parallel to the incline.

(b)   It is mg cos θ is perpendicular to the incline.

4 .    The definition of work is work = force times parallel displacement.

The work-energy principle states that W NC = (ΔKE ) + (ΔPE )

5 .    Only forces acting on an object and that have a single, specific source can go on free-body diagrams. Some of the things that cannot go on a free-body diagram but that students often put there by mistake include the following:

6 .    Impulse is force times time interval, and also change in momentum. Impulse has units either of newton·seconds or kilogram·meters/second.

7 .    Momentum is conserved in all collisions. Kinetic energy is conserved only in elastic collisions.

8 .    Using the reasoning from question #1, if weight is mg , then m = W /g .

9 .    The acceleration of a projectile is always g ; i.e., 10 m/s2 , downward. Even though the velocity is instantaneously zero, the velocity is still changing, so the acceleration is not zero. (By the way, the answer “−10 m/s2 ” is wrong unless you have clearly and specifically defined the down direction as negative for this problem.)

10 .    The magnitude of the resultant force is found by placing the component vectors tip-to-tail. This gives a right triangle, so the magnitude is given by the Pythagorean theorem, 50 N. The angle of the resultant force is found by taking the inverse tangent of the vertical component over the horizontal component, tan−1 (40/30). This gives the angle measured from the horizontal.

11 .    

friction force divided by normal force. μ has no units.

12 .    Acceleration is the slope of a velocity-time graph.

13 .    Displacement is the area under a velocity-time graph (i.e., the area between the graph and the horizontal axis).

14 .    Velocity is the slope of a position-time graph. If the position-time graph is curved, then instantaneous velocity is the slope of the tangent line to the graph.

15 .    Because acceleration is not zero, the object cannot be moving with constant speed. If the signs of acceleration and velocity are the same (here, if velocity is positive), the object is speeding up. If the signs of acceleration and velocity are different (here, if velocity is negative), the object is slowing down.

16 .    An object always moves in the direction indicated by the velocity.

17 .    If the gravitational field g is known, mg gives the gravitational force. Newton’s law of gravitation, Gm 1 m 2 /r 2 , is valid everywhere in the universe.

18 .    An object in uniform circular motion experiences a centripetal , meaning “center-seeking,” force. This force must be directed to the center of the circle.

19 .    This and all three kinematics equations are valid only when acceleration is constant. So, for example, this equation cannot be used to find the distance traveled by a mass attached to a spring. The spring force changes as the mass moves; thus, the acceleration of the mass is changing, and kinematics equations are not valid. (On a problem where kinematics equations aren’t valid, conservation of energy usually is what you need.)

20 .    Angular momentum is conserved when no torques act on a system other than torques due to objects within the system itself.

21 .    Rotational inertia I is an object’s innate resistance to a change in its angular velocity. For an object that can be treated as a point mass, I = mr 2 , where m is the object’s mass and r is the distance from the center of rotation. For multiple objects, add the rotational inertias of each object together to get the total.

Electricity

22 .    

23 .    Current

24 .    Voltage

25 .    Voltage

26 .    Current

27 .    Power

Waves

28 .    

29 .    Open at both ends. The standing wave in such a pipe is symmetric, with a node at both ends (or an antinode at both ends).

30 .    They are reciprocals—the period is 1/f .

31 .    Frequency and wavelength

32 .    Wavelength, λ . The length of the string doesn’t change, and the wavelength is related to the length of the string. The speed v changes because the string is tightened, increasing the wave speed; the frequency f changes because a tighter string causes a higher pitch.