PHY 2140Exam 3PHY 2140Date, 2003Please type your name here Please type your student number here Instructions:The following procedure must be followed in order to correct any (unlikely) mistakes in the grading. 1. Do all the questions. Show your work for partial credit. I must be able to understand what you have done while I am reading the exam – not when you explain it to me after the exam is graded and returned.2. For each problem: (a) write down any formula(s) used(b) justify why you used that particular formula(s)(c) copy the answer you have circled from the exam pages to the General Purpose Answer Sheet and fill in the ovals. (d) show your work! No work – no point.3. The formula sheet is on the last page of the exam. You may detach it from the rest of the exam. I read and understood the statement aboveYour signatureRow:Seat:NAME1. An inductor has a 54 Ohm reactance at 60 Hz. What will be the peak current if this inductoris connected to a 50 Hz source that produces 100 V rms voltage?a. 0.69 Ab. 1.41 Ac. 2.71 Ad. 3.14 Ae. none of the above2. An inductor and a resistor are connected in series. When connected to a 60 Hz, 80 V source, the voltage drop across the resistor is found to be 35 V rms and the power dissipated in the circuit is 11 W. What is the value of the resistance? a. 97 b. 111 c. 123 d. 134 e. 151 f. 167 3. If a 2.0 H inductor is used in a tuning circuit in a radio, what is the capacitance needed to tune in Phat Matt on 89X at a frequency of 88.7 MHz?a. 0.54 pFb. 0.71 pFc. 0.91 pFd. 1.61 pFe. That station sucks!NAME4. A new elementary particle is detected. Moving with a speed of 0.98c, the lifetime of the particle is measured to be 1.3 x 10-7 s by a stationary observer. What is its proper lifetime?a. 1.12 x 10-9 sb. 2.45 x 10-9 sc. 4.52 x 10-9 sd. 6.02 x 10-9 se. 2.59 x 10-8 s5. Marilyn Monroe and Albert Einstein go for a ride in a rocket ship at a speed of 0.7c. Albert finds that Marilyn’s heart beats 90 times per minute (I think she likes him). What is her heart rate according to a stationary observer on the Earth? Hint: what is the time interval between heart beats?a. 36 beats/minb. 64 beats/minc. 122 beats/mind. 160 beats/mine. zero beats per minute 6. Stephen Hawking and Albert Einstein each blast off in rockets, labeled “e” and “h” in the figure. In a cosmic game of “chicken,” they fly towards one another on a collision course. Each rocket has a speed of 0.8c as measured by a stationary observer on the Earth. What is the speed of Einstein’s rocket as measured by Hawking?a. zerob. 0.26cc. 0.74cd. 0.98ce. 1.60ceehhNAME7. A radio wave has a frequency of 5.00 MHz. Find its wavelength.a. 60 mmb. 15 mmc. 60 md. 15 me. zero8. If the total energy of a rocket ship is three times its rest energy, what is its speed?a. 0.63cb. 0.72cc. 0.94cd. 0.99c e. none of the above9. The phasor diagrams below represent three oscillating emfs having different amplitudes and frequencies at a certain instant of time t =0. As t increases, each phasor rotates counterclockwise and completely determines a sinusoidal oscillation. At the instant of time shown, the magnitude of E associated with each phasor given in ascending order by diagrams? a. a, b, cb. b, c, ac. a, c, b d. c, b, ae. need more info10. Radio The light bulb has a resistance R, and the emf drives the circuit with a frequency . The light bulb glows most brightly at a. Very low frequenciesb. Very high frequencies c. Resonant frequency11. A supertrain of proper length 100 m travels at a speed of 0.95c as it passes through a tunnel having proper length 50 m. As seen by a trackside observer, is the train ever completely within the tunnel? a. yesb. noc. halfwayd. not enough informatione. what are you talking about?12. (bonus) Imagine that the entire Sun collapses to a sphere of radius Rg such that the work required to remove a small mass m from the surface would be equal to its rest energy, mc2. This radius is called the gravitational radius for the Sun. Find Rg. (It is believed that the ultimate fate of very massive stars is to collapse beyond their gravitational radii into black holes.) a. 3347 kmb. 127 kmc. 1.47 kmd. 1.14 me. impossible to find22mmVVII IRVR, , CCIXV LLIXV CfXC21fLXL2 22CLXXRZ IZV RXXCLtancosVIPavLCf21fc 2211cvPtt PLL mvp21cvvvvvCBACCBACAB2mcE22mcmcKE 42222cmcpE c = 3.00 x 10c = 3.00 x 1088 m/s m/sh = 6.63 x 10h = 6.63 x 10nhfEnhfKEmaxKmT 2max102989.01 eV = 1.6 x 101 eV = 1.6 x
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