# Mastering Physics Set 2 Midterm #1

## Unlock all answers in this set

question
A glass marble is rubbed against a piece of silk. As a result the piece of fabric acquires extra electrons. What happens to the glass marble? Check all that apply. The marble has lost the same number of electrons acquired by the piece of silk. The marble has acquired the same number of electrons acquired by the piece of silk. The marble acquires a positive charge and repels the piece of silk. The marble acquires a positive charge and attracts the piece of silk. The marble acquires a negative charge and attracts the piece of silk. The marble acquires a negative charge and repels the piece of silk.
The marble has lost the same number of electrons acquired by the piece of silk. The marble acquires a positive charge and attracts the piece of silk.
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has not been in contact with the piece of fabric, which of the following statements best describes the situation when the three marbles are brought together? To keep things simple in this Tutorial, we will ignore the effects of polarization and just focus on the overall charge of each object. Marbles 1 and 2 attract each other, but no interaction occurs with marble 3. Both marbles 1 and 2 attract marble 3. The three marbles will repel each other. Marbles 1 and 2 repel each other, but no interaction occurs with marble 3.
Marbles 1 and 2 repel each other, but no interaction occurs with marble 3.
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strongly attractive
(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls A and B? strongly attractive strongly repulsive weakly attractive neither attractive nor repulsive
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weakly attractive
(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls A and C? strongly attractive strongly repulsive weakly attractive neither attractive nor repulsive
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attractive
(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls A and D? attractive repulsive neither attractive nor repulsive
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neither attractive nor repulsive
(Figure 1) Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together. What is the nature of the force between balls D and C? attractive repulsive neither attractive nor repulsive
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negative
The net electric force on the blue sphere has a magnitude F and is directed in the ? y direction. What is the sign of the charge on the yellow sphere? positive negative
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positive
The net electric force on the blue sphere has a magnitude F and is directed in the ? y direction. What is the sign of the charge on the red sphere? positive negative
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qred = q?2(d1/d2)^2cos(?)
The net electric force on the blue sphere has a magnitude F and is directed in the ? y direction. Suppose that the magnitude of the charge on the yellow sphere is determined to be 2q. Calculate the charge qred on the red sphere. Express your answer in terms of q, d1, d2, and ?.
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C
Along which of the lines (A to H) in (Figure 1) should charge 2 be placed so that the free-body diagrams of charge 1 and charge 2 are consistent? Note that only one of the forces on each charge will be consistent. The other force on each charge will be addressed in Part B with the introduction of charge 3.
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D
Along which of the lines (A to H) in (Figure 2) should charge 3 be placed so that the free-body diagrams of charge 1, charge 2, and charge 3 are consistent?
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H
Along which of the lines (A to H) in (Figure 3) should charge 2 be placed so that the free-body diagrams of charge 1 and charge 2 are consistent? Note that only one of the forces on each charge will be consistent. The other force on each charge will be addressed in Part D with the introduction of charge 3.
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F
Along which lines (A to H) in (Figure 4) should charge 3 be placed so that the free-body diagrams of charge 1, charge 2, and charge 3 are consistent?
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D
Which of the following panels (labelled A, B, C, and D) in (Figure 2) correctly depicts the field lines from an infinite uniformly negatively charged sheet? Note that the sheet is being viewed edge-on in all pictures. A B C D
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Field lines cannot cross each other. The field lines should be parallel because of the sheet's symmetry
In (Figure 2) , what is wrong with panel B? (Pick only those statements that apply to panel B.) Check all that apply. Field lines cannot cross each other. The field lines should be parallel because of the sheet's symmetry. The field lines should spread apart as they leave the sheet to indicate the weakening of the field with distance. The field lines should always end on negative charges or at infinity.
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B
Which of the following panels (labelled A, B, C, and D) in (Figure 3) shows the correct electric field lines for an electric dipole? A B C D
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The field lines should be smooth curves. The field lines should always end on negative charges or at infinity.
In (Figure 3) , what is wrong with panel D? (Pick only those statements that apply to panel D.) Check all that apply. Field lines cannot cross each other. The field lines should turn sharply as you move from one charge to the other. The field lines should be smooth curves. The field lines should always end on negative charges or at infinity.
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QA=+7q, QB=?3q
In (Figure 4) , the electric field lines are shown for a system of two point charges, QA and QB. Which of the following could represent the magnitudes and signs of QA and QB? In the following, take q to be a positive quantity. QA=+q, QB=?q QA=+7q, QB=?3q QA=+3q, QB=?7q QA=?3q, QB=+7q QA=?7q, QB=+3q
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A=D>F>C>B=E
In the diagram below, there are three collinear point charges: q1, q2, and q3. The distance between q1 and q2 is the same as that between q2 and q3. You will be asked to rank the Coulomb force on q1 due to q2 and q3
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Force on q3 = -6.05ร10^?5N
What is the net force exerted by these two charges on a third charge q3 = 54.5 nC placed between q1 and q2 at x3 = -1.210 m ? Your answer may be positive or negative, depending on the direction of the force. Express your answer numerically in newtons to three significant figures.
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6.58ร10^?13 N
Find the magnitude of the electric force, ignoring the sign, that the water molecule exerts on the chlorine ion.
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negative x
What is the direction of the electric force? negative x positive x
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attractive
Is this force attractive or repulsive? attractive repulsive
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Four equal negative point charges are located at the corners of a square, their positions in the xy-plane being (1,1), (?1,1), (?1,?1), (1,?1). The electric field on the x-axis at (1,0) points in the same direction as i^. j^. ?i^ ?j^
?i^
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The electric field produced by the positive charge is directed radially toward the charge at all locations near the charge. wraps circularly around the positive charge. is directed radially away from the charge at all locations near the charge.
is directed radially away from the charge at all locations near the charge.
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Now, let's look at how the distance from the charge affects the magnitude of the electric field. Select Show numbers on the green menu, and then click and drag one of the orange E-Field Sensors. You will see the magnitude of the electric field given in units of V/m (volts per meter, which is the same as newtons per coulomb). Place the E-Field Sensor 1 m away from the positive charge (1 m is two bold grid lines away if going in a horizontal or vertical direction), and look at the resulting field strength. Consider the locations to the right, left, above, and below the positive charge, all 1 m away. For these four locations, the magnitude of the electric field is: greatest below the charge. greatest to the left of the charge. the same. greatest to the right of the charge. greatest above the charge.
the same.
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What is the magnitude of the electric field 1 m away from the positive charge compared to the magnitude of the electric field 2 m away? The magnitude of the electric field 1 m away from the positive charge is- two times equal to one-quarter four times one-half - the magnitude of the electric field 2 m away.
four times
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If the field strength is E = 9 V/m a distance of 1 m from the charge, what is the field strength E a distance of 3 m from the charge?
E = 1 V/m
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Remove the positive charge by dragging it back to the basket, and drag a negative charge (blue) toward the middle of the screen. Determine how the electric field is different from that of the positive charge. Which statement best describes the differences in the electric field due to a negative charge as compared to a positive charge? The electric field changes direction (now points radially inward), but the electric field strength does not change. Nothing changes; the electric field remains directed radially outward, and the electric field strength doesnรขt change. The electric field changes direction (now points radially inward), and the magnitude of the electric field decreases at all locations
The electric field changes direction (now points radially inward), but the electric field strength does not change.
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drag two positive charges, placing them 1 m apart, as shown below. Letรขs look at the resulting electric field due to both charges. Recall that the electric field is a vector, so the net electric field is the vector sum of the electric fields due to each of the two charges. Where is the magnitude of the electric field roughly equal to zero (other than very far away from the charges)? The electric field is nonzero everywhere on the screen. The electric field is roughly zero near the midpoint of the two charges. The electric field is zero at any location along a vertical line going through the point directly between the two charges
The electric field is roughly zero near the midpoint of the two charges.
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Consider a point 0.5 m above the midpoint of the two charges. As you can verify by removing one of the positive charges, the electric field due to only one of the positive charges is about 18 V/m. What is the magnitude of the total electric field due to both charges at this location? 36 V/m 25 V/m zero
25 V/m
question
Make an electric dipole by replacing one of the positive charges with a negative charge, so the final configuration looks like the figure shown below. The electric field at the midpoint is zero. directed to the left. directed to the right.