Deck 19: Electric Forces and Electric Fields

Question 1

A particle (m = 50 g,q = 5.0 $\mu$ C)is released from rest when it is 50 cm from a second particle (Q = -20 $\mu$ C).Determine the magnitude of the initial acceleration of the 50-g particle.

A)54 m/s²
B)90 m/s²
C)72 m/s²
D)65 m/s²
E)36 m/s²

Answer 1

72 m/s²

Question 2

If a = 3.0 mm,b = 4.0 mm,Q₁ = 60 nC,Q₂ = 80 nC,and q = 24 nC in the figure,what is the magnitude of the electric force on q?

A)2.7 N
B)1.9 N
C)2.3 N
D)1.5 N
E)0.52 N

Answer 2

1.5 N

Question 3

A point charge Q is placed on the x axis at x = -2.0 m.A second point charge,-Q,is placed at x = 1.0 m.If Q = 60 $\mu$ C,what is the magnitude of the electrostatic force on a 40- $\mu$ C charge placed at the origin?

A)16 N
B)27 N
C)32 N
D)11 N
E)3.0 N

Answer 3

27 N

Question 4

If a = 3.0 mm,b = 4.0 mm,Q₁ = 60 nC,Q₂ = 80 nC,and q = 32 nC in the figure,what is the magnitude of the electric force on q?

A)1.6 N
B)1.3 N
C)1.9 N
D)2.2 N
E)0.040 N

Question 5

Three pith balls supported by insulating threads hang from a support.We know that ball X is positively charged.When ball X is brought near balls Y and Z without touching them,it attracts Y and repels Z.Since pith is an insulating material,we can conclude that

A)Y has a negative charge.
B)Z has a negative charge.
C)Y has a positive charge.
D)Z has a positive charge.
E)Z is neutral (has no net charge. )

Question 6

Three point charges are positioned on the x axis.If the charges and corresponding positions are +32 $\mu$ C at x = 0,+20 $\mu$ C at x = 40 cm,and -60 $\mu$ C at x = 60 cm,what is the magnitude of the electrostatic force on the +32- $\mu$ C charge?

A)84 N
B)12 N
C)36 N
D)50 N
E)48 N

Question 7

A particle (charge = +40 $\mu$ C)is located on the x axis at the point x = -20 cm,and a second particle (charge = -50 $\mu$ C)is placed on the x axis at x = +30 cm.What is the magnitude of the total electrostatic force on a third particle (charge = -4.0 $\mu$ C)placed at the origin (x = 0)?

A)41 N
B)16 N
C)56 N
D)35 N
E)72 N

Question 8

A point charge Q is placed on the x axis at x = 2.0 m.A second point charge,-Q,is placed at x = 3.0 m.If Q = 40 $\mu$ C,what is the magnitude of the electrostatic force on a 30- $\mu$ C charge placed at the origin?

A)7.2 N
B)3.9 N
C)1.5 N
D)14 N
E)8.1 N

Question 9

If a = 3.0 mm,b = 4.0 mm,Q₁ = 60 nC,Q₂ =-80 nC,and q = 36 nC in the figure,what is the magnitude of the electric force on q?

A)5.0 N
B)4.4 N
C)3.8 N
D)5.7 N
E)0.60 N

Question 10

Rubber rods charged by rubbing with cat fur repel each other.Glass rods charged by rubbing with silk repel each other.A rubber rod and a glass rod charged respectively as above attract each other.A possible explanation is that

A)Any two rubber rods charged this way have opposite charges on them.
B)Any two glass rods charged this way have opposite charges on them.
C)A rubber rod and a glass rod charged this way have opposite charges on them.
D)All rubber rods always have an excess of positive charge on them.
E)All glass rods always have an excess of negative charge on them.

Question 11

Enrico says that positive charge is created when you rub a glass rod with silk,and that negative charge is simply the absence of positive charge.Rosetta says that negative charge is created and that positive charge is the absence of positive charge.(She has heard that Ben Franklin should have reversed the signs he associated with the charges. )Which one,if either,is correct?

A)Enrico,because there really is only one kind of charge.
B)Rosetta,because there really is only one kind of charge.
C)Neither: although no charge is present originally,both types of charge are created through friction.
D)Both: only one type of charge is created by friction at any one time.
E)Neither: both negative and positive charge are present simultaneously in all solid materials on Earth and the process described involves a transfer of charge,not the creation of charge.

Question 12

Three point charges,two positive and one negative,each having a magnitude of 20 $\mu$ C are placed at the vertices of an equilateral triangle (30 cm on a side).What is the magnitude of the electrostatic force on the negative charge?

A)80 N
B)40 N
C)69 N
D)57 N
E)75 N

Question 13

A charge of +80 $\mu$ C is placed on the x axis at x = 0.A second charge of -50 $\mu$ C is placed on the x axis at x = 50 cm.What is the magnitude of the electrostatic force on a third charge of 4.0 $\mu$ C placed on the x axis at x = 30 cm?

A)13 N
B)77 N
C)39 N
D)25 N
E)45 N

Question 14

An uncharged metal sphere is placed on an insulating puck on a frictionless table.While being held parallel to the table,a rod with a charge q is brought close to the sphere,but does not touch it.As the rod is brought in,the sphere

A)remains at rest.
B)moves toward the rod.
C)moves away from the rod.
D)moves perpendicular to the velocity vector of the rod.
E)moves upward off the puck.

Question 15

Each of two small non-conducting spheres is charged positively,the combined charge being 40 $\mu$ C.When the two spheres are 50 cm apart,each sphere is repelled from the other by a force of magnitude 2.0 N.Determine the magnitude of the smaller of the two charges.

A)1.4 $\mu$ C
B)1.1 $\mu$ C
C)2.0 $\mu$ C
D)3.3 $\mu$ C
E)17 $\mu$ C

Question 16

If a = 3.0 mm,b = 4.0 mm,Q₁ = -60 nC,Q₂ = 80 nC,and q = 30 nC in the figure,what is the magnitude of the electric force on q?

A)1.4 N
B)1.0 N
C)1.7 N
D)2.0 N
E)0.50 N

Question 17

Two identical pith balls supported by insulating threads hang side by side and close together,as shown below. One is positively charged;the other is neutral.We can conclude that

A)all field lines leaving the positively charged pith ball end on the neutral pith ball.
B)some of the field lines leaving the positively charged pith ball end on the neutral pith ball.
C)none of the field lines leaving the positively charged pith ball end on the neutral pith ball.
D)positive charge is transferred along the field lines until both balls have equal charges.
E)positive charge is transferred along the field lines until both balls hang along vertical lines.

Question 18

In the figure,if Q = 30 $\mu$ C,q = 5.0 $\mu$ C,and d = 30 cm,what is the magnitude of the electrostatic force on q?

A)15 N
B)23 N
C)zero
D)7.5 N
E)38 N

Question 19

A point charge Q is placed on the x axis at the origin.An identical point charge is placed on the x axis at x = -1.0 m and another at x = +1.0 m.If Q = 40 $\mu$ C,what is the magnitude of the electrostatic force on the charge at x = +1.0 m?

A)29 N
B)14 N
C)11 N
D)18 N
E)7.0 N

Question 20

Three pith balls supported by insulating threads hang from a support.We know that ball X is positively charged.When ball X is brought near balls Y and Z without touching them,it attracts Y and repels Z.Since pith is an insulating material,we can conclude that

A)Y has a negative charge.
B)Z has a negative charge.
C)Y has a positive charge.
D)Z is neutral (has no net charge. )
E)Y is negatively charged or neutral (has no net charge. )

Question 21

If Q = 20 $\mu$ C and L = 60 cm,what is the magnitude of the electrostatic force on any one of the charges shown?

A)25 N
B)19 N
C)15 N
D)9.1 N
E)14 N

Question 22

If a = 60 cm,b = 80 cm,Q = -6.0 nC,and q = 3.0 nC in the figure,what is the magnitude of the electric field at point P?

A)71 N/C
B)56 N/C
C)60 N/C
D)53 N/C
E)67 N/C

Question 23

If a = 60 cm,b = 80 cm,Q = -4.0 nC,and q = 1.5 nC,what is the magnitude of the electric field at point P?

A)68 N/C
B)72 N/C
C)77 N/C
D)82 N/C
E)120 N/C

Question 24

If a = 60 cm,b = 80 cm,Q = -6.0 nC,and q = 4.0 nC,what is the magnitude of the electric field at point P?

A)35 N/C
B)42 N/C
C)52 N/C
D)64 N/C
E)104 N/C

Question 25

Three 2.50 $\mu$ C charges are placed on tiny conducting spheres at the ends of 1.00 m-long strings that are connected at 120 $\degree$ angles as shown below.The magnitude,in N,of the tension in any one of the strings is

A)1.88 * 10 ^{- 2}.
B)3.25*10 ^{- 2}.
C)3.75* 10 ^{- 2}.
D)6.50 *10 ^{- 2}.
E)7.50*10 ^{- 2}.

Question 26

Two charged particles,Q₁ and Q₂,are a distance r apart with Q₂ = 5Q₁.Compare the forces they exert on one another when $\overrightarrow { \mathrm { F } } _ { 1 }$ is the force Q₂ exerts on Q₁ and $\overrightarrow { \mathrm { F } } _ { 2 }$ is the force Q₁ exerts on Q₂.

A) $\overrightarrow { \mathrm { F } } _ { 2 }$ = 5 $\overrightarrow { \mathrm { F } } _ { 1 }$ .
B) $\overrightarrow { \mathrm { F } } _ { 2 }$ = -5 $\overrightarrow { \mathrm { F } } _ { 1 }$ .
C) $\overrightarrow { \mathrm { F } } _ { 2 }$ = $\overrightarrow { \mathrm { F } } _ { 1 }$ .
D) $\overrightarrow { \mathrm { F } } _ { 2 } = - \overrightarrow { \mathrm { F } } _ { 1 }$
E)5 $\overrightarrow { \mathrm { F } } _ { 2 }$ = $\overrightarrow { \mathrm { F } } _ { 1 }$ .

Question 27

If Q = 16 nC,a = 3.0 m,and b = 4.0 m,what is the magnitude of the electric field at point P?

A)33 N/C
B)31 N/C
C)24 N/C
D)19 N/C
E)13 N/C

Question 28

The symbol $\frac { 1 } { 4 \pi \varepsilon _ { 0 } }$ appears in Coulomb's law because we use independently defined units for

A)force and distance.
B)charge and distance.
C)distance and force.
D)force,distance and electric charge.
E)charge.

Question 29

Two tiny metal spheres are fixed to the ends of a non-conducting string of length $\ell$ .Equal charges,+q,are placed on the metal spheres.Randall says that the force on the string has magnitude $\frac { 1 } { 2 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ .Tilden says that the tension in the string has magnitude $\frac { 1 } { 2 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ .Which one,if either,is correct?

A)Randall,because both charges exert forces on the string,but the tension is $\frac { 1 } { 4 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ .
B)Tilden,because both charges exert forces on the string,but the net force is $\frac { 1 } { 4 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ .
C)Both are correct,because both charges exert forces on the string.
D)Neither is correct,because both the tension and the force have magnitude $\frac { 1 } { 4 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ .
E)Neither is correct,because the tension is $\frac { 1 } { 4 \pi \varepsilon _ { 0 } } \frac { q ^ { 2 } } { \ell ^ { 2 } }$ ,but the net force is 0.

Question 30

If a = 60 cm,b = 80 cm,Q = -6.0 nC,and q = 6.0 nC,what is the magnitude of the electric field at point P in the figure?

A)65 N/C
B)55 N/C
C)60 N/C
D)52 N/C
E)67 N/C

Question 31

Three point charges,two positive and one negative,each having a magnitude of 20 $\mu$ C are placed at the vertices of an equilateral triangle (30 cm on a side).What is the magnitude of the electrostatic force on one of the positive charges?

A)69 N
B)40 N
C)80 N
D)57 N
E)20 N

Question 32

If Q = 25 $\mu$ C,q = 10 $\mu$ C,and L = 40 cm in the figure,what is the magnitude of the electrostatic force on q?

A)28 N
B)22 N
C)20 N
D)14 N
E)10 N

Question 33

A point charge Q is placed at the origin.A second charge,2Q,is placed on the x axis at x = -3.0 m.If Q = 50 $\mu$ C,what is the magnitude of the electrostatic force on a third point charge,-Q,placed on the y axis at y = +4.0 m?

A)2.5 N
B)3.0 N
C)3.7 N
D)4.4 N
E)1.8 N

Question 34

Three identical point charges Q are placed at the vertices of an equilateral triangle (length of each side = 2.0 m).If Q = 60 $\mu$ C,what is the magnitude of the electrostatic force on any one of the charges?

A)25 N
B)19 N
C)14 N
D)22 N
E)16 N

Question 35

Identical point charges Q are placed at each of the four corners of a 3.0 m * 4.0 m rectangle.If Q = 40 $\mu$ C,what is the magnitude of the electrostatic force on any one of the charges?

A)3.0 N
B)2.4 N
C)1.8 N
D)3.7 N
E)2.0 N

Question 36

A +15-nC point charge is placed on the x axis at x = 1.5 m,and a -20-nC charge is placed on the y axis at y = -2.0m.What is the magnitude of the electric field at the origin?

A)105 N/C
B)15 N/C
C)75 N/C
D)45 N/C
E)60 N/C

Question 37

A point charge (-5.0 $\mu$ C)is placed on the x axis at x = 4.0 cm,and a second charge (+5.0 $\mu$ C)is placed on the x axis at x = -4.0 cm.What is the magnitude of the electric force on a third charge (+2.5 $\mu$ C)placed on the y axis at y = 3.0 cm?

A)90 N
B)45 N
C)54 N
D)72 N
E)36 N

Question 38

Three 2.50 $\mu$ C charges are placed on tiny conducting spheres at the ends of 1.00 m-long strings that are connected at 120 $\degree$ angles as shown below.The magnitude,in N,of the force on any one of the charges is

A)1.88 * 10 ^{- 2}.
B)3.25 * 10 ^{- 2}.
C)3.73 *10 ^{- 2}.
D)6.50 *10 ^{- 2}.
E)7.50 * 10 ^{- 2}.

Question 39

A +2.0-nC point charge is placed at one corner of a square (1.5 m on a side),and a -3.0-nC charge is placed on a corner diagonally away from the first charge.What is the magnitude of the electric field at either of the two unoccupied corners?

A)20 N/C
B)14 N/C
C)4.0 N/C
D)12 N/C
E)8.0 N/C

Question 40

If Q = 80 nC,a = 3.0 m,and b = 4.0 m in the figure,what is the magnitude of the electric field at point P?

A)45 N/C
B)70 N/C
C)29 N/C
D)47 N/C
E)92 N/C

Question 41

A uniform linear charge of 3.0 nC/m is distributed along the y axis from y = -3 m to y = 2m.Which of the following integrals is correct for the magnitude of the electric field at y = 4 m on the y axis?

A) $\int _ { - 3 } ^ { 2 } \frac { 27 d y } { ( 4 - y ) ^ { 2 } }$
B) $\int _ { - 3 } ^ { 2 } \frac { 27 d y } { 16 + y ^ { 2 } }$
C) $$\int _ { - 3 } ^ { 2 } \frac { 135 d y } { ( 4 - y ) ^ { 2 } }$$
D) $\int _ { - 3 } ^ { 2 } \frac { 135 d y } { 16 + y ^ { 2 } }$
E)none of these

Question 42

A charge Q is placed on the x axis at x = +4.0 m.A second charge q is located at the origin.If Q = +75 nC and q = -8.0 nC,what is the magnitude of the electric field on the y axis at y = +3.0 m?

A)19 N/C
B)23 N/C
C)32 N/C
D)35 N/C
E)21 N/C

Question 43

A 40- $\mu$ C charge is positioned on the x axis at x = 4.0 cm.Where should a -60- $\mu$ C charge be placed to produce a net electric field of zero at the origin?

A)-5.3 cm
B)5.7 cm
C)4.9 cm
D)-6.0 cm
E)+6.0 cm

Question 44

Which one of the diagrams below is not a possible electric field configuration for a region of space which does not contain any charges?

A)
B)
C)
D)
E)

Question 45

A 24-nC charge is distributed uniformly along the x axis from x = 2 m to x = 6 m.Which of the following integrals is correct for the magnitude (in N/C)of the electric field at x = +8 m on the x axis?

A) $$\int _ { 2 } ^ { 6 } \frac { 54 d x } { ( 8 - x ) ^ { 2 } }$$
B) $\int _ { 2 } ^ { 6 } \frac { 216 d x } { ( 8 - x ) ^ { 2 } }$
C) $\int _ { 2 } ^ { 6 } \frac { 54 d x } { x ^ { 2 } }$
D) $$\int _ { 2 } ^ { 6 } \frac { 216 d x } { x ^ { 2 } }$$
E)none of these

Question 46

A 12-nC charge is distributed uniformly along the y axis from y = 0 to y = 4 m.Which of the following integrals is correct for the x component of the electric field at x = 2 m on the x axis?

A) $\int _ { 0 } ^ { 4 } \frac { 216 d y } { \left( 4 + y ^ { 2 } \right) ^ { 3 / 2 } }$
B) $\int _ { 0 } ^ { 4 } \frac { 54 d y } { \left( 4 + y ^ { 2 } \right) ^ { 3 / 2 } }$
C) $\int _ { 0 } ^ { 4 } \frac { 108 d y } { 4 + y ^ { 2 } }$
D) $\int _ { 0 } ^ { 4 } \frac { 27 d y } { 4 + y ^ { 2 } }$
E)none of these

Question 47

A uniform linear charge of 2.0 nC/m is distributed along the x axis from x = 0 to x = 3 m.Which of the following integrals is correct for the x component of the electric field at y = 2 m on the y axis?

A) $$\int _ { 0 } ^ { 3 } \frac { - 18 x d x } { \left( 4 + x ^ { 2 } \right) ^ { 3 / 2 } }$$
B) $\int _ { 0 } ^ { 3 } \frac { - 18 d x } { ( 2 + x ) ^ { 2 } }$
C) $\int _ { 0 } ^ { 3 } \frac { - 18 d x } { 4 + x ^ { 2 } }$
D) $\int _ { 0 } ^ { 3 } \frac { - 18 x d x } { ( 2 + x ) ^ { 3 } }$
E)none of these

Question 48

A charge of 80 nC is uniformly distributed along the x axis from x = 0 to x = 2.0 m.Determine the magnitude of the electric field at a point on the x axis with x = 8.0 m.

A)30 N/C
B)15 N/C
C)48 N/C
D)90 N/C
E)60 N/C

Question 49

A uniformly charged rod (length = 2.0 m,charge per unit length = 3.0 nC/m)is bent to form a semicircle.What is the magnitude of the electric field at the center of the circle?

A)64 N/C
B)133 N/C
C)48 N/C
D)85 N/C
E)34 N/C

Question 50

A +20-nC point charge is placed on the x axis at x = 2.0 m,and a -25-nC point charge is placed on the y axis at y = -3.0 m.What is the direction of the electric field at the origin?

A)209 $\degree$
B)61 $\degree$
C)29 $\degree$
D)241 $\degree$
E)151 $\degree$

Question 51

A uniformly charged rod (length = 2.0 m,charge per unit length = 5.0 nC/m)is bent to form one quadrant of a circle.What is the magnitude of the electric field at the center of the circle?

A)62 N/C
B)56 N/C
C)50 N/C
D)44 N/C
E)25 N/C

Question 52

Charge of uniform density 4.0 nC/m is distributed along the x axis from x = -2.0 m to x = +3.0 m.What is the magnitude of the electric field at the point x = +5.0 m on the x axis?

A)16 N/C
B)13 N/C
C)19 N/C
D)26 N/C
E)5.0 N/C

Question 53

A charge of 50 nC is uniformly distributed along the y axis from y = 3.0 m to y = 5.0 m.What is the magnitude of the electric field at the origin?

A)18 N/C
B)50 N/C
C)30 N/C
D)15 N/C
E)90 N/C

Question 54

A charge of 25 nC is uniformly distributed along a circular arc (radius = 2.0 m)that is subtended by a 90-degree angle.What is the magnitude of the electric field at the center of the circle along which the arc lies?

A)81 N/C
B)61 N/C
C)71 N/C
D)51 N/C
E)25 N/C

Question 55

A uniform linear charge density of 7.0 nC/m is distributed along the y axis from y = 2 m to y = 5 m.Which of the following integrals is correct for the magnitude (in N/C)of the electric field at y = 0 on the y axis?

A) $\int _ { 2 } ^ { 5 } \frac { 63 d y } { y ^ { 2 } }$
B) $$\int _ { 2 } ^ { 5 } \frac { 21 d y } { y ^ { 2 } }$$
C) $\int _ { 2 } ^ { 5 } \frac { 63 d y } { ( 5 - y ) ^ { 2 } }$
D) $\int _ { 2 } ^ { 5 } \frac { 21 d y } { ( 5 - y ) ^ { 2 } }$
E)none of these

Question 56

A uniform linear charge of 2.0 nC/m is distributed along the x axis from x = 0 to x = 3 m.What is the x component of the electric field at y = 2 m on the y axis?

A)-5.0 N/C
B)-4.0 N/C
C)-5.7 N/C
D)-6.2 N/C
E)-9.0 N/C

Question 57

A uniform linear charge of 2.0 nC/m is distributed along the x axis from x = 0 to x = 3 m.Which of the following integrals is correct for the y component of the electric field at y = 4 m on the y axis?

A) $$\int _ { 0 } ^ { 3 } \frac { 72 d x } { \left( 16 + x ^ { 2 } \right) ^ { 3 / 2 } }$$
B) $$\int _ { 0 } ^ { 3 } \frac { 18 d x } { \left( 16 + x ^ { 2 } \right) ^ { 3 / 2 } }$$
C) $\int _ { 0 } ^ { 3 } \frac { 72 d x } { 16 + x ^ { 2 } }$
D) $\int _ { 3 } ^ { 0 } \frac { 18 d x } { 16 + x ^ { 2 } }$
E)none of these

Question 58

A charge (uniform linear density = 9.0 nC/m)is distributed along the x axis from x = 0 to x = 3.0 m.Determine the magnitude of the electric field at a point on the x axis with x = 4.0 m.

A)81 N/C
B)74 N/C
C)61 N/C
D)88 N/C
E)20 N/C

Question 59

A 16-nC charge is distributed uniformly along the x axis from x = 0 to x = 4 m.Which of the following integrals is correct for the magnitude (in N/C)of the electric field at x = +10 m on the x axis?

A) $\int _ { 0 } ^ { 4 } \frac { 36 d x } { ( 10 - x ) ^ { 2 } }$
B) $\int _ { 0 } ^ { 4 } \frac { 154 d x } { ( 10 - x ) ^ { 2 } }$
C) $\int _ { 0 } ^ { 4 } \frac { 36 d x } { x ^ { 2 } }$
D) $\int _ { 6 } ^ { 10 } \frac { 154 d x } { x ^ { 2 } }$
E)none of these

Question 60

A rod (length = 2.0 m)is uniformly charged and has a total charge of 40 nC.What is the magnitude of the electric field at a point which lies along the axis of the rod and is 3.0 m from the center of the rod?

A)40 N/C
B)45 N/C
C)24 N/C
D)90 N/C
E)36 N/C

Question 61

A particle (q = 4.0 mC,m = 50 g)has a velocity of 25 m/s in the positive x direction when it first enters a region where the electric field is uniform (60 N/C in the positive y direction).What is the speed of the particle 5.0 s after it enters this region?

A)49 m/s
B)35 m/s
C)32 m/s
D)44 m/s
E)24 m/s

Question 62

A particle (mass = 5.0 g,charge = 40 mC)moves in a region of space where the electric field is uniform and is given by E_x =-2.3 N/C,E_y = E_z = 0.If the position and velocity of the particle at t = 0 are given by x = y = z = 0 and v_z = 20 m/s,v_x = v_y = 0,what is the distance from the origin to the particle at t = 2.0 s?

A)60 m
B)54 m
C)69 m
D)78 m
E)3.2 m

Question 63

A particle (mass = 5.0 g,charge = 40 mC)moves in a region of space where the electric field is uniform and is given by E_x = -5.5 N/C,E_y = E_z = 0.If the position and velocity of the particle at t = 0 are given by x = y = z = 0 and v_x = 50 m/s,v_y = v_z = 0,what is the distance from the origin to the particle at t = 2.0 s?

A)60 m
B)28 m
C)44 m
D)12 m
E)88 m

Question 64

Charges q and Q are placed on the x axis at x = 0 and x = 2.0 m,respectively.If q = -40 pC and Q = +30 pC,determine the net flux through a spherical surface (radius = 1.0 m)centered on the origin.

A)-9.6 N . m²/C
B)-6.8 N . m²/C
C)-8.5 N .m²/C
D)-4.5 N.m²/C
E)-1.1 N .m²/C

Question 65

Two charges of 15 pC and -40 pC are inside a cube with sides that are of 0.40-m length.Determine the net electric flux through the surface of the cube.

A)+2.8 N. m²/C
B)-1.1 N .m²/C
C)+1.1 N. m²/C
D)-2.8 N . m²/C
E)-0.47 N . m²/C

Question 66

A particle (m = 20 mg,q = -5.0 $\mu$ C)moves in a uniform electric field of 60 N/C in the positive x direction.At t = 0,the particle is moving 25 m/s in the positive x direction and is passing through the origin.How far is the particle from the origin at t = 2.0 s?

A)80 m
B)20 m
C)58 m
D)10 m
E)30 m

Question 67

The velocity of a particle (m = 10 mg,q = -4.0 $\mu$ C)at t = 0 is 20 m/s in the positive x direction.If the particle moves in a uniform electric field of 20 N/C in the positive x direction,what is the particle's speed at t = 5.0 s?

A)60 m/s
B)20 m/s
C)45 m/s
D)40 m/s
E)70 m/s

Question 68

A positively charged particle is moving in the +y-direction when it enters a region with a uniform electric field pointing in the +x-direction.Which of the diagrams below shows its path while it is in the region where the electric field exists.The region with the field is the region between the plates bounding each figure.The field lines always point to the right.The x-direction is to the right;the y-direction is up.

A)
B)
C)
D)
E)

Question 69

In a diagram of charges and electric field lines charge $Q _ { 1 }$ has twelve field lines going outward from it and charge $Q _ { 2 }$ has three field lines going into it.If one of the charges is 100 nC,what is the other one?

A)25 nC
B)100 nC
C)-25 nC
D)-100 nC
E)Both answers b and c can be correct.

Question 70

A particle (mass = 5.0 g,charge = 40 mC)moves in a region of space where the electric field is uniform and is given by E_x = 2.5 N/C,E_y = E_z = 0.If the velocity of the particle at t = 0 is given by v_y = 50 m/s,v_x = v_z = 0,what is the speed of the particle at t = 2.0 s?

A)81 m/s
B)72 m/s
C)64 m/s
D)89 m/s
E)25 m/s

Question 71

A particle (m = 20 mg,q = -5.0 $\mu$ C)moves in a uniform electric field of 60 N/C in the positive x direction.At t = 0,the particle is moving 30 m/s in the positive x direction and is passing through the origin.Determine the maximum distance beyond x = 0 the particle travels in the positive x direction.

A)25 m
B)20 m
C)15 m
D)30 m
E)60 m

Question 72

When a positive charge q is placed in the field created by two other charges Q₁ and Q₂,each a distance r away from q,the acceleration of q is

A)in the direction of the charge Q₁ or Q₂ of smaller magnitude.
B)in the direction of the charge Q₁ or Q₂ of greater magnitude.
C)in the direction of the negative charge if Q₁ and Q₂ are of opposite sign.
D)in the direction of the positive charge if Q₁ and Q₂ are of opposite sign.
E)in a direction determined by the vector sum of the electric fields of Q₁ and Q₂.

Question 73

Suppose a uniform electric field of 4 N/C is in the positive x direction.When a charge is placed at and fixed to the origin,the resulting electric field on the x axis at x = 2 m becomes zero.What is the magnitude of the electric field at x = 4 m on the x axis at this time?

A)0
B)1 N/C
C)2 N/C
D)4 N/C
E)More information is needed to find the resulting field magnitude at this position.

Question 74

When gravitational,magnetic and any forces other than static electric forces are not present,electric field lines in the space surrounding a charge distribution show

A)the directions of the forces that exist in space at all times.
B)only the directions in which static charges would accelerate when at points on those lines
C)only the directions in which moving charges would accelerate when at points on those lines.
D)tangents to the directions in which either static or moving charges would accelerate when passing through points on those lines.
E)the paths static or moving charges would take.

Question 75

Two uniform rods,each of length 2.0 m,are bent to form semicircles.One rod has a charger per unit lent of 1.5 nC/m,and the other has a charge per unit length of -1.5 nC/m.The semicircles are joined to make a circle.What is the magnitude of the electric field at the center of the circle?

A)42 N/C
B)84 N/C
C)34 N/C
D)68 N/C
E)0

Question 76

A particle (mass = 4.0 g,charge = 80 mC)moves in a region of space where the electric field is uniform and is given by E_x =-2.5 N/C,E_y = E_z = 0.If the velocity of the particle at t = 0 is given by v_x = 80 m/s,v_y = v_z = 0,what is the speed of the particle at t = 2.0 s?

A)40 m/s
B)20 m/s
C)60 m/s
D)80 m/s
E)180 m/s

Question 77

The total electric flux through a closed cylindrical (length = 1.2 m,diameter = 0.20 m)surface is equal to-5.0 N . m²/C.Determine the net charge within the cylinder.

A)-62 pC
B)-53 pC
C)-44 pC
D)-71 pC
E)-16 pC

Question 78

A particle (q = 3.0 mC,m = 20 g)has a speed of 20 m/s when it enters a region where the electric field has a constant magnitude of 80 N/C and a direction which is the same as the velocity of the particle.What is the speed of the particle 3.0 s after it enters this region?

A)68 m/s
B)44 m/s
C)56 m/s
D)80 m/s
E)36 m/s

Question 79

A negatively charged particle is moving in the +x-direction when it enters a region with a uniform electric field pointing in the +x-direction.Which graph gives its position as a function of time correctly? (Its initial position is x = 0 at t = 0. )

A)
B)
C)
D)
E)

Question 80

A charge of 50- $\mu$ C is placed on the y axis at y = 3.0 cm and a 77- $\mu$ C charge is placed on the x axis at x = 4.0 cm.If both charges are held fixed,what is the magnitude of the initial acceleration of an electron released from rest at the origin?

A)1.2 *10²⁰ m/s²
B)1.5 *10²⁰ m/s²
C)1.0 * 10²⁰ m/s²
D)1.8 *10²⁰ m/s²
E)2.0 * 10²⁰ m/s²