AP Physics 2: Electrostatics and Newton's Laws Quiz

The figure shows two identical, initially uncharged conducting spheres. Sphere B is grounded and sphere A is not grounded. A positively charged rod is brought close to but does not touch sphere A as shown. The rod is then removed. A student claims that both spheres are now charged. Is the student correct? Why or why not?

• Yes. When the rod is brought near, both spheres become negatively charged.

• Yes. The ground on sphere B ensures that there is no movement of charge on either sphere when the rod is removed

• No. When the rod is brought near, sphere A is polarized and sphere B gains a net negative charge. When the rod is removed, sphere B remains charged but sphere A does not remain polarized.

• No. When the rod is removed, the situation is identical to before the rod was brought near, so both spheres are uncharged.

An electric charge Q is placed at the origin. A charge q is placed at point B and the force on charge q due to charge Q is F. What is the force on charge q if charge q is moved to point A?

• 4F

• 2F

• F/4

• F/2

Two identical conducting spheres are charged to +Q and -3Q and separated by a distance r. The attractive force between the spheres is F. The two spheres are brought in a brief contact and then moved to the original positions. If the new electrostatic force between the spheres is F’, which of the following is true?

• F' = F

• F' = 3F

• F' = F/3

• F' = 9F

Two charged spheres, X and Y, are held fixed at two vertices of a triangle, as shown. The direction of the electric field E at the third vertex due to the two spheres is also shown. Which of the following best represents a closeup view of the equipotential lines near the third vertex of the triangle?

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• 
• 
• 

A point charge of −q is located at (x, 0), and a point charge of +q is located at (−x, 0), as shown. The magnitude of the electric field created by one of these point charges at the point (0, y), which is a distance r from each point charge, is E. What is the magnitude and direction of the electric field created by both point charges at the point (0, y) ?

An electron (charge e) is released from rest at point P in an electric field whose equipotential lines are shown in the figure. What is the kinetic energy of the electron when it reaches point Q ? Ignore gravitational effects.

• 0

At time t=0s, object XXof mass M travels at a constant speed of 2 m/s to the right toward object Y of mass 2M that is a distance of 8m away from object X while at rest, as shown above. Both objects are on a horizontal surface, where the frictional forces may be considered negligible. Which of the following pairs of force diagrams represents the forces exerted on object X and object Y at t=4 s?

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• 
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• 

An Atwood’s machine is set up by suspending two blocks connected by a string of negligible mass over a pulley, as shown above. The blocks are initially held at rest and then released at time t0=0  The speed of the 3 kg block at time t1=2.0 s is most nearly

• 2 m/s

• 4 m/s

• 7 m/s

• 10 m/s

An object is released from a large height above the ground and takes a very long time to reach the ground. The only forces exerted on the object are the force of Earth's gravity and the force of friction exerted by Earth’s atmosphere as the object falls. A graph of the object’s speed v as a function of time t is shown above. Which of the following claims best describes the force of friction exerted on the object?

• It is initially zero and increases until it is equal to the force of gravity.

• It is initially equal to the force of gravity and decreases until it is zero.

• It is always equal to the force of gravity.

• It is always greater than the force of gravity.