Download Uconn Physics Spring 2007 Exam

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UConn Physics 122 Spring 2007 Final Exam
Do 8 of the 10 questions below. You must indicate which two problems you do not want graded.
1. Two particles, with identical positive charges and a separation of 2.60 cm, are released from rest.
Immediately after release, particle 1 has an acceleration whose magnitude is 4.60 km/s2, while particle
2 has an acceleration in the opposite direction whose magnitude is 8.5 km/s2. Particle 1 has a mass of
6.00 x 10-6 kg. Find
a) the charge on each particle
b) the mass of particle 2
2. An object with a net charge of +24 microcoulombs is placed in a uniform electric field of 610 N/C,
directed vertically upward. What is the mass of the object if it “floats” (Hint: there is gravity) in this
electric field?
b) A free electron and a free proton (not connected to an atom) are placed in an identical electric field.
Compare the electric force and the resulting accelerations experienced by each particle.
3. Three capacitors C1=5.00 microFarads, C2=4.00 microFarads, and C3=9.00 microFarads are
connected together. Find the effective capacitance of the group if they are connected in parallel
b) If they are connected in series.
4. A particular light bulb is rated at 60 Watts using 120 V household voltage. How much current does
this light bulb draw? What is the resistance of the bulb is at its power rating?
b) Use Kirchhoff’s rules to find the current through each of the resistors in the circuit shown below.
4.0 
2.0 
5.0 
4.0 V
2.0 
1.0 
5. A charge of -8.3 microcoulombs is traveling at a speed of 7.4 x 106 m/s in a region of space where
the there is a magnetic field. The angle between the velocity of the charge and the field is 52 degrees.
A force of magnitude 5.4 x 10-3 N acts on the charge. What is the magnitude of the magnetic field?
6. A particular double slit interference experiment causes red light with a wavelength of 700 nm to
form a second order bright spot at an angle of 20 degrees. What is the space between the slits?
b) An object 3.00 cm high is placed 20.0 cm from a convex mirror, with a focal length of 8.00 cm.
Find the position of the final image, the magnification of the mirror and the height of the image.
7. A 31.0 cm diameter coil consists of 20 turns of circular copper wire 2.6 mm in diameter. A uniform
magnetic field, perpendicular to the plane of the coil, changes at a rate of 8.65 x 10-3 T/s. Determine
(i)the induced emf (voltage) and (ii) the current in the loop and (iii)the rate at which thermal energy is
produced
b) An ac generator consists of eight turns of wire with an area of 0.0900 m2 with a total resistance of
12.0 ohms. The loops rotate in a magnetic field of 0.500 T at a constant frequency of 60.0 hz. What
are the maximum induced emf and the maximum current?
8. a) Write down the two postulates of Einstein’s Special Theory of Relativity.
b) A friend of yours travels by you in her fast sports car at a speed of 0.580 c. You measure the
vehicle to 5.80 m long and 1.20 m high, (while she is moving and you are at rest)
a) What would be its length and height if you measured the sports car when is was at rest?
b) How many seconds would you say have elapsed on your friends when 20.0 seconds have passed on
yours?
9. When UV light of wavelength 225 nm falls on a metal surface, the maximum Kinetic Energy of the
emitted photoelectrons is 1.40 eV. What are the work function and the cut-off wavelength of the
incident light for this metal?
b) Show that if an electron and a proton have the same non-relativistic kinetic energy, the proton has
the shorter deBroglie wavelength?
10. Because it has the highest binding energy (Eb) per nucleon of all nuclides, 6228Ni is regarded as the
most strongly bound nucleus. Its neutral atomic mass is 61.928349 u. Find its mass defect, its total
binding energy and its binding energy per nucleon. The mass of a neutral Hydrogen atom is 1.007825
u and that of a neutron is 1.008665 u. Also 1.00 u = 931.5 MeV/c2.
b) The radioactive nuclide 199Pt has a half life of 30.8 minutes. A 10 g sample of platinum nuclides is
prepared. How many 199Pt nuclei are initially present in the sample?
c) How many are present 92.4 minutes after the sample is first prepared?