PhysicsBowl 2019 (Part 2) Printer Friendly Version
26. A 15.0-mW laser emits a beam that is 2.00 mm in diameter. What is the intensity of this beam?
27. The unit that is used to measure magnetic flux is:
28. A curve on a racetrack has a radius of 80 m and is banked at 45°. Suppose that the road surface on the curve somehow became frictionless (perhaps caused by an ice storm or an oil spill) and a car needs to navigate this curve. What is the safe speed with which to take the curve without either sliding up or down the bank of the curve?
29. A convex lens has a focal length of 50 mm. How far from the lens must an object be placed if it is to form a virtual image magnified in size by a factor of three?
30. Consider the bicycle wheel shown below to be a ring with a 60 cm diameter and a mass of 1.5 kg. Attached to the wheel is a gear with a radius of 4.0 cm and negligible mass. A force of 20 N is applied tangentially to the gear for 4.0 s. Starting from rest, what linear speed does the wheel achieve, assuming it rolls without slipping?

31. The intensity level is measured to be 60 dB at a distance of 15 m from a speaker. What is the intensity level at a point 2.0 m from the speaker? Assume that the speaker radiates equally in all directions
32. A pine wood block is floating in a small pool. There is a second pine wood block that sits on top of the first and does not touch the water. If the top block is taken off and placed in the water, how does the new water level in the pool compare to the original water level?
33. Two cars are being tested on a track. Car 1 accelerates from rest on this straight track at a1= 3.0m/s2. Two seconds later, Car 2 accelerates from rest at a2= 12.0 m/s2. How much time after Car 1 starts will Car 2 pass Car 1?
34. The table shown below lists the finish times for the 2008 Men’s Olympic 100 m butterfly swim final in Beijing. From the data, what is the best estimate of the distance the 2nd place finisher, Cavic, was behind the 1st place finisher, Phelps?

35. In a mixture of hydrogen, oxygen, and nitrogen gases at room temperature, the molecules having the greatest average speed are those of
The next two questions share the same information Base your answers to questions 36 and 37 on the Circuit 2. The battery is assumed ideal with an emf of 3.0 V.

36. The resistor that dissipates the most power is:
37. The voltage across resistor R4 is:
38. Shown is accelerometer data for an elevator ride in a skyscraper in Chicago. The spikes at roughly 10s and 72s are caused by the handling of the accelerometer which rested on the floor of the elevator and occurred before the elevator started moving up, and after it reached the top, respectively. What is the best estimate for the peak vertical speed for this elevator?

39. The picture shows two speakers, A and B, which emit the same 680-Hz tones in phase. Point P is located 1.000 m directly in front of Speaker A. A sound sensor at Point P records a minimum sound intensity. Speaker B is slowly moved away from Speaker A along the line joining them. How far must Speaker B be moved further from Speaker A until the sound sensor at Point P first records a maximum sound intensity?

40. The bulb of a mercury thermometer has a volume of 0.100 cm3 at 10oC and contains 0.100 cm3 of mercury. The capillary tube above the bulb has a cross-sectional area of 0.012 mm2. The volume thermal expansion coefficient of mercury is 1.8 × 10-4 (Co)-1. How much will the mercury rise when the temperature rises by 30 Co (the expansion of the glass is negligible)?

All Division 1 students STOP HERE. Your last answer should be for #40. Numbers #41-#50 should remain blank for Division 1 students.
All Division 2 students continue to Questions #41 – #50.

41. To monitor the breathing of a hospital patient, a thin belt is wrapped around a patient’s chest and back. The belt is a 200 turn coil of conducting wire. When the patient inhales, the area of the coil increases by 39.0 cm2. The magnitude of the Earth’s magnetic field is 50.0 μT and makes an angle of 28.0o to the plane of the coil. Assuming the patient takes 1.80 s to inhale, how much emf is induced in the coil?
42. Three identical samples of a monatomic ideal gas are taken from a temperature T to a temperature 2T. Sample A undergoes an adiabatic process. Sample B undergoes an isobaric process and Sample C undergoes an isochoric process. Which of the following correctly ranks the heats added to the samples during the three processes?
43. Two boxes are stacked on a table as shown at right. The mass of box 1 is m and the mass of box 2 is 3m. The surface between box 2 and the table is smooth and the surface between the two boxes is rough. When a force, F, is applied, box 1 does not slide on box 2. What is the minimum coefficient of static friction between the boxes?

44. Consider a traveling wave on a string of length L, mass M, and tension T. A standing wave is set up. Which of the following is true?

45. A heat engine is operating between 40°C and 380°C and has an efficiency that is 60% of a Carnot engine that is operating between the same temperatures. If the engine absorbs heat at a rate of 60 kW, at what rate does it exhaust heat?
46. In physics experiments located deep underground, the two types of cosmic rays that most commonly reach the experimental apparatus are:

47. When two identical resistors are connected in series to an ideal voltage source, the current supplied by the source is 2.0 Amperes. When these two resistors are connected in parallel to the same ideal voltage source, what is the current supplied by the source?
48. It is observed that a charged particle moves through a region of space and experiences no magnetic force. From this we can conclude that

49. A lump of clay whose rest mass is 4.0 kg is traveling at three-fifths of the speed of light when it collides head-on with an identical lump going in the opposite direction at the same speed. If the two lumps stick together and no energy is radiated away, what is the mass of the composite lump?
50. One mole of ideal gas initially at temperature T0 and volume V0 undergoes a reversible isothermal expansion to V1. If the ratio of specific heats is cp/cv = γ and if R is the gas constant, then the work done by the gas is:

All Division 2 students STOP HERE. Your last answer should be for #50.