PhysicsLAB AAPT Quiz
1994 Physics Olympiad Screening Test (Part 2)

16. A simple pendulum of length L and mass m is attached to a moving support.
 
 
In order for the pendulum string to make a constant angle θ with the vertical, the support must be moving to the:




 
17. A Carnot cycle takes in 1000 J of heat at a high temperature of 400 K. How much heat is expelled at the cooler temperature of 300 K?
 
18. An ideal gas is expanded at constant pressure from initial volume Vi and temperature Ti to final volume Vf and temperature Tf. The gas has molar heat capacity CP at constant pressure. The amount of work done by n moles of the gas during the process can be expressed:
 
19. The average translational kinetic energy of any ideal gas depends only on:




 
20. A soap film of thickness t is surrounded by air. It is illuminated at near normal incidence by monochromatic light which has wavelength λ in the film.
 

A film thickness of ____ will produce maximum brightness of the reflected light.
 
21. You are given two lenses, a converging lens with focal length +10 cm and a diverging lens with focal length –20 cm. Which of the following would produce a real image that is smaller than the object?




 
22. A source at rest emits waves with wavelength λ in a medium with velocity v. If the source moves to the right with velocity vs, the distance between adjacent crests λ’ directly behind the source is:
 
 
23. Two sources, in phase and a distance d apart, each emit a wave of wavelength λ. See accompanying figure.
 
 
Which of the choices for the path difference ΔL = L1 – L2 will always produce constructive interference at point P?
 
Refer to the following information for the next two questions.

Two point charges of +4.00 µC and –9.00 µC are placed 1.00 m apart, as shown in the accompanying figure.
 
 
Assume the potential goes to zero as R goes to infinity.
24. The total electric field due to the two charges is zero at a point:




 
25. How much work is done moving the –9.00 µC charge from its original position to a new position 2.00 m from the +4.00 µC charge?
 
26. A point charge Q is placed at the center of a spherical conducting shell, the shaded part of the accompanying figure. A total charge of –q is placed on the shell.
 
The magnitude of the electric field at point P1 a distance R1 from the center is ____. The magnitude of the electric field at point P2 a distance R2 from the center is ____.
 
27. R4, as shown in the figure, is a variable resistor.
 

In order for there to be no current through the ammeter, R4 must be equal to:
 
28. A resistor R dissipates power P when connected directly to a voltage source V, as shown in the accompanying figures.
 

What resistance R' must be connected in series with R to decrease the power dissipated in R to ½P?
 
29. The infinitely long straight wire carries a conventional current I as shown in the accompanying figure. The rectangular loop carries a conventional current I' in the counterclockwise direction.
 

The net force on the rectangular loop is:




 
30. A spatially uniform magnetic field of 0.080 T is directed into the plane of the page and perpendicular to it, as shown in the accompanying figure. A wire loop in the plane of the page has constant area 0.010 m2. The magnitude of the magnetic field decreases at a constant rate of 3.0 x 10–4 T/s.
 

What is the magnitude and direction of the induced emf?




 




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