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Physics Seat P202
R. Heinz/R. de Ruyter
EXAM #4
May 5, 2004 8:0010:00 AM
INSTRUCTIONS 1. Please indicate with form (1, 2, 3, or 4) exam you have by marking the appropriate bubble in column P of the SPECIAL CODES box on your answer sheet. Your exam is form 1. 2. Sit in SEAT # given above. 3. DO NOT OPEN THE EXAM UNTIL YOU ARE TOLD TO DO SO. 4. Print your name (last name first) and blacken in the letters on the answer sheet with a #2 pencil. 5. Print your student number (identification number) and blacken in the numbers on the answer sheet with a #2 pencil. 6. Use the fronts and backs of the question sheets for scratch work. Do not use any other scratch sheets. 7. This is a multiple choice exam. Blacken in the answer to each question on the answer sheet. Fill in one and only one answer to each question. 8. Keep your eyes on your own work. 9. You have two hours to complete the exam. When you finish, please show your picture ID as you turn in your answer sheet. Please leave quietly so others are not disturbed. 10. THERE ARE 24 QUESTIONS PLEASE ANSWER ALL OF THEM. THERE IS NO PENALTY FOR GUESSING!
This is a closed book, closed note exam! You may use only a calculator and four self-prepared sheets of formulas.
=============================================================== Table of useful constants: (Speed of light in vacuum)2: Plancks constant: Product of h and c: Electron rest energy: Proton rest energy: c2 = 931.494 MeV / u h = 6.626 10-34 J s = 4.136 10-15 eV s h c = 1.986 10-25 J m = 1240 eV nm me c2 = 0.511 MeV mp c2 = 938.272 MeV
=============================================================== A linear charge distribution has a charge per unit length . When the perpendicular distance from this distribution is tripled, what happens to the electric field strength? a. b. c. d. e. 2 It increases by a factor of (3)1/2. It decreases by a factor of (3)1/2. It increases by a factor of 3. It decreases by a factor of 3. It stays the same.
1.
Charges of +25 C, -9 C, and +25 C are located along a horizontal line. Neighboring charges are separated by 4 m, as shown in the sketch. What is the magnitude of the force on either 25 C charge due to the two other charges?
+25 C
-9 C
+25 C
4m
4m
a. b. c. d. e.
38.610-3 N 34.110-3 N 31.210-3 N 27.610-3 N 23.610-3 N
3.
Choose the incorrect statement from the five statements below. a. The velocity of light is independent of the velocity of the observer and the source b. The velocity of light is constant irrespective of the medium through which it is traveling. c. The velocity of light in a vacuum is larger than the velocity of light in glass. d. The velocity of light in a vacuum does not depend on the wavelength of light. e. The velocity of light in a vacuum is the same as the velocity of x-rays in a vacuum.
4.
An unstable particle called the pion has a mean lifetime of 25 ns in its own rest frame. A beam of pions travels through the laboratory at a speed of 0.80c. What is the mean lifetime of the pions as measured in the laboratory frame? a. b. c. d. e. 12 ns 22 ns 32 ns 42 ns 52 ns
5.
A spaceship flies directly over a football field, from one goal line to the other, at a speed of 0.60c, as observed on Earth. If the length of the field between goal lines in the Earth frame is 91.5 m (100 yards), what length is observed by the pilot of the spaceship? a. b. c. d. e. 93.2 m 88.2 m 83.2 m 78.2 m 73.2m
6.
A man on the Moon observes two spaceships coming toward him from opposite directions at speeds of 0.60c and 0.80c. What is the relative speed of the two ships as measured by a passenger on either one of the spaceships? a. b. c. d. e. .2c .862c .946c .975c 1.2c
7.
A straight, stiff wire of length 1.00 m and mass 25 g is suspended horizontally in a magnetic field B 0.75 T. The magnetic field lines are perpendicular to the wire (see figure below). The wire is connected to an emf. How much current must flow in the wire so that the force on the wire exactly compensates the force due to the Earths gravitational pull? Use g=9.8 m/s2.
a. b. c. d. e.
75 mA 327 mA 0.025 mA 101 mA 6200 mA
8.
A relativistic electron has a total energy of 0.65 MeV. What is its momentum (in MeV/c)? a. b. c. d. e. 0.50 MeV/c 0.35 MeV/c 0.30 MeV/c 0.44 MeV/c 0.40 MeV/c
9.
Which of these statements correctly describe the images formed by an object placed before a single thin lens? 1. Real are images always enlarged. 2. Real images are always inverted. 3. Virtual images are always upright. 4. Convex lenses never produce virtual images. a. b. c. d. e. 1 and 3 are correct, 2 and 4 are false 2 and 3 are correct, 1 and 4 are false 2 and 4 are correct, 1 and 3 are false 2, 3, and 4 are correct, 1 is false 1, 2, and 3 are correct, 4 is false
=
10.
Photons of energy 4.2 eV bombard a surface, which emits photoelectrons with kinetic energies for 0 to 1.8 eV. What is the threshold frequency for this surface?
11.
An x-ray tube produces photons down to a 0.0827 nm wavelength. What is the accelerating potential for this tube? a. b. c. d. e. 123 kV 9.22 kV 8.00 kV 10.0 kV 15.0 kV
12.
In a Compton scattering experiment, the scattered photon has a wavelength of 6.55 pm. If the scattering angle is 50o, what is the wavelength of the incident photon? a. b. c. d. e. 5.68 pm 8.42 pm 3.28 pm 6.55 pm 2.43 pm
13.
What is the wavelength of a photon emitted when an electron in hydrogen goes from the n = 4 state to the n = 1 state? a. b. c. d. e. 323 nm 156 nm 121 nm 103 nm 97.3 nm
a. b. c. d. e.
1.3 5.8 1.3 7.7 7.7
1014 Hz 1014 Hz 1015 Hz 1014 Hz 1015 Hz
14.
A particle is incident from the left on a slit of width w and the particle passes through the slit opening (see figure below). The uncertainty principle restricts which of these quantities?
a. the product of the width w and the minimum possible uncertainty in the y-component of the particles momentum b. the product of the width w and the minimum possible uncertainty in the x-component of the particles momentum c. the product of the width w and the minimum possible uncertainty in the z-component of the particles momentum d. the product of the width w and the minimum possible de Broglie wavelength of the particle e. the maximum possible width w
15.
If an electron is accelerated from rest through a potential difference of 100 V, what is its de Broglie wavelength?
a. b. c. d. e.
1.20 10 15 m 8.67 10 9 m 0.529 10 10 m 1.23 10 10 m 2.55 10 9 m
16.
The Pauli exclusion principle a. states that two electrons in the same atom cannot have identical sets of quantum numbers. b. states that two electrons in the same atom cannot have the same orbits. c. states that two electrons in the same atom cannot have the same spin angular momentum d. excludes electrons from atomic nuclei. e. excludes protons from electron orbits.
17.
A particle confined in a box, with ground state energy E1 = 4 eV, undergoes a transition from the second excited state to the third excited state by absorbing a photon. What is the energy of the photon? a. b. c. d. e. 4 eV 16 eV 20 eV 28 eV 260 eV
18.
A capacitor and a resistor are connected through a switch to an emf (see figure). At the instant just after the switch is closed
a. b. c. d. e.
The current in the circuit is zero. The voltage across the capacitor is E. The voltage across the resistor is zero. The voltage across the resistor is E. The voltages across the resistor and across the capacitor are each E.
19.
What is the binding energy of 12 C ? The mass of an atom of 12 C is 12 u (exactly), 6 6 of an atom of 1H is 1.007825 u, and of a neutron is 1.0086649 u. a. b. c. d. e. 137 MeV 104 MeV 92.2 MeV 46.1 MeV 7.68 MeV
20.
226 88
Ra decays by alpha decay. What are A and Z for the daughter nuclide?
a. b. c. d. e.
226, 92 222, 92 226, 88 222, 88 222, 86
21.
The half-life of 30P is 2.50 minutes. If a sample of 30P has 1.60 x 1010 nuclei present initially, after 10.0 minutes how many nuclei remain?
a. b. c. d. e.
2.88716 u 3.01605 u 3.03494 u 3.04221 u 2.99982 u
22.
The fusion reaction 2H + 3H 4He + 1n releases 17.6 MeV of energy. The mass of 2H is 2.01410 u, the mass of 4He is 4.00260 u, and the mass of 1n is 1.00866 u. What is the mass of 3H? (All masses are atomic masses.)
a. b. c. d. e.
0.80 0.40 0.20 0.10 0.05
1010 1010 1010 1010 1010
23.
The figure indicates a circuit in which the resistors and EMFs are not shown. The currents in the six independent circuit segments are shown. Which of the following equations is correct?
a. b. c. d. e.
I5 + I6 = I1 I3 + I6 = I4 I1 + I2 + I3 = 0 I2 + I4 + I5 = 0 I2 + I5 = I4
24.
A lamp with resistance 60 Ohm carries an electric current of 1.5 A. What potential difference is applied across the lamp? a. b. c. d. e. 90 Volt 60 Volt 120 Volt 30 Volt 220 Volt