General Physics II (PHYS 104)Exam 1: February 23,2012

a) 1m/s

a)3.54,. 10*3 Wlm2c) 8.25 x 10-3 Wm2e) 1.05 x 10-2 Wlm2

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Multiple Choice (4 points each): Answer the following multiple choice questions. Clearly circlethe response (or responses) that provides the best answer to the question. If you desire, neatlyand briefly show any calculations or reasoning off to the side. This work may be considered inthe evaluation of the exam.

1) The distance befween the crest of a water wave and the next trough is 2 m. If the frequency of

A=,lrra particular wave is 2Hz, what is the speed of the wave?

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2) A rnass of 0.40 kg, hanging from a spring with a spring constant of 80.0 N/m, is set into an

up-and-down simple harmonic motion. If the mass is displaced from equilibrium by 0.10 mand released from rest, what is its speed when moving through the equilibrium point?

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3) The sound intensity level of a jet plane going down the runway as observed from a certainlocation is 105 dB. What is the intensity of the sound at this location?

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4) When two tuning forks are sounded at the same time, a beat frequency of 5 Hz occurs. If one

of the tuning forks has a frequency of 245 Hz, what is the frequency of the other tuning fork?(There may be more than one correct answer.)

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5) If an object of mass m attachedto a light spring is replaced by one of mass 9m,the frequency

of the vibrating system changes by what multiplicative factor? r*L = L, ,ly.

a) 3.0 b) 6.0 ) il" v rh

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6) Analuminumnailhasanexcesscharge of +3.2 pC.Howmanyelectronsmustbeaddedto

Two uncharged conducting spheres, A and B, are suspended from insulating threads so thatthey touch each other. While a negatively charged rod is held near, but not touching sphere

A, the two spheres are separated. How will the spheres be charged, if at all?

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8) A very small ball has a mass of 5.0 x10-3 kg and a charge of 4.0 pC. What magnitude electric

field directed upward will balance the weight of the ball?

r"****""'.-**/9) A -4.0 pC charge is located 0.30 m to the left of a 6 pC charge. What is the maguitude and

direction of the electrostatic force on the positive charge?c) 4.8 N to the rightd) 4.8 N to the left

e) 7.2 N to the right

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the nail,to._zukg it electrically neutral?

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c) 2.0 x 10'' d) 3.2x

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e) 5.0 x 10-14

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a) 8.2 x102 N/Cc) 2.0 xl0-2 N/Ce) 5.t xt06 N/C

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10) At which point (or points) is the electric field zero lJ/C for the two point charges shown on

the.x axis? $f -#l; ti' **+4q -2q f .l o =;f+{h,-*e

x

a) The electric field is never zero inthe vicinity of these charges.

b) The electric field is zero somewhere on the x axis to the left of the +4q charge.

ffrffr. electric field is zero somewhere on the x axis to the right of the -2q charge.

Tfn" electric field is zero somewhere on the x axis between the two charges, but this

point is nearer to the -2q charge.

e) The electric field is zero at two points along the x axis; one such point is to the right

of the -2q charge and the other is to the left of the +4q charge.

Questions and Problems: Provide clear and logical answers to questions 1 and 2 rydeitherquestion 3 or 4. Where calculations are required, neatly show all work. You must clearly show

all work to receive fu1l credit. Be sure that your answers have the correct units. If you continue

your work on another sheet of paper, be sure that it is clearly labeled. Be sure to include FB and

other diagrams where appropriate, A/r1 d/

1 (20 Points) A block oscillates on a spring with a spring constant of 20 N/m a period of 3.0 s.

The kinetic energy of the block as it passes through equilibrium is 25'0 J.

a) Determine the frequency of the oscillation.b) Determine the mass of the block.c) Find the maximum speed of the block during the oscillation.d) What is the amplitude of the oscillation?e) What is the maximum acceleration of the block?f) Describe the relationship between velocity and acceleration during on complete oscillation.

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2 (20 points) Four point charges are placed A *r ' Dat the corners of a square as shown in the

figure. Each side of the square has length 2.0 VAm. Determine the magnitude of the electric ( 5field at the center of the square. The point P \y fiat the center of the square is a distanc e 1.414 +\m from each of the four corners. k== AfrC O @ - ftr, = -e n C

a) For each of the four charges on the corners, draw a vector representing the eiectric fie1d at the

center of the square.

b) For each charge calculate the magnitude of the electric field it produces at the center of the

square.

cjlete.-ine the magnitude of the total electric field at the center of the square. In what direction

is the electric field pointing

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3 (20 points) A guitar sking with a linear density of 2.0 grn/mis stretched between supports that

are 60 cm apart. The speed of the wave in the string is measured to be 16.8 m/s.

a) Find the tension in the string?

b) If a standing wave forms when the string is vibrating with a frequency of 840'Hz, how

many antinodes are observed?

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4 (20 ponts) A sound meter located 2.0 mfrom a loud speaker measures an intensity of 2.0x10-a

Wlm2.

a) Determine the power output of the loud speaker.

b) Find the intensity measured by the sound meter when it is located 8.0 m from the source.

c) Determine and compare the sound intensity level (in decibels) at the two locations.

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