 PhysicsBowl 2015 (Part 2) Printer Friendly Version
26. The position of a mass connected to a spring obeys 𝑥(𝑡)=𝐴cos(𝜔𝑡). What is the average speed of the mass for one full oscillation in terms of the mass’ maximum speed during oscillation, vmax?
The next two questions share the same information Base your answers to questions 27 and 28 on the information and diagram below.

 On a frictionless horizontal surface, two bodies make a head-on collision and stick together. Body 1 has a mass of 3.50 kg and initially moves to the right with speed 7.0 m/s. Body 2 is initially is at rest. A graph of the force exerted onto Body 2 from Body 1 during the collision is shown. 27. What is the mass of Body 2?
28. How much kinetic energy was transformed to other kinds of energy from the collision? 29. An electron moves at constant non-zero velocity directly between two long straight wires. The conventional current in each wire has the same magnitude, but the currents are in opposite directions as shown in the figure. Ignoring gravity, which choice best reflects the direction of the magnetic field and the direction of the electric field that exist at the location of the electron? Any electric field in the region originates from an unseen external source. 30. A spring scale reads 2.50 N when a small solid mass hangs from it in air. The spring scale reads 1.58 N when the mass at the end of the spring is completely submerged in a container of water. Which one of the following choices best represents the density of the solid mass?
31. Approximately how many hydrogen atoms are there in the liquid water of Earth’s oceans?
32. An object moving along a line completes a 20.0 second trip with an average speed of 10.0 m/s in two stages. During stage 1, the object moves with a constant velocity of 6.0 m/s to the right for 12.0 seconds. What constant magnitude acceleration directed to the left must the object have during the 8.0 seconds of stage 2? 33. Two spherical speakers separated by 30.0 m each emit a constant frequency signal of 57.0 Hz in phase with each other. The speed of sound is 342 m/s. How many locations of complete destructive interference of the incoming signals are there on the line between the speakers?
34. An upward-pointing object is placed 15.0 cm to the left of a lens system. The first lens is convex with focal length 10.0 cm. The second lens is convex with focal length 10 cm and its location from the first lens is varied from 10 cm away to 110 cm away. Which one of the following choices best represents the description of the final image formed as the second lens is moved from x = 10 cm to x = 110 cm from the first lens?  35. Two uniform disks, X and Y, have equal masses, M, but different radii such that rX < rY. Both disks initially are at rest. A force F is applied tangent to each disk at its right edge for the same amount of time. As a result, each disk rotates counterclockwise in the plane of the page about a fixed frictionless axis through its center.

Which one of the following choices correctly compares the magnitudes of angular momentum L about the center axis and total kinetic energy K of disk X and disk Y?
36. Rain falls vertically at 12.0 m/s with respect to a stationary observer. A car is moving at an angle of 40° below the horizontal with respect to the observer. A passenger sitting in the car notes that the rain makes an angle of 29.0° with the vertical. What is the car's speed with respect to the observer?
37. Which one of the following choices represents the base SI units of inductance? 38. A thin film of alcohol (nalcohol = 1.35) lies on a flat glass surface (nglass = 1.60). When light of wavelength 540 nm is incident normal to the alcohol surface from air, the light is strongly reflected, but when light of wavelength 432 nm is incident normal to the surface from air, the reflected light is minimized. Which one of the following choices could represent the thickness, t, of the alcohol film?
39. For the circuit shown, the four light bulbs have identical resistance, the battery is ideal and all wires have no resistance. After the switch, S, in the circuit is closed, which one of the following choices correctly describes what happens to the magnitude of the current at the point labeled P and to the magnitude of the potential difference from W to X?  40. A 2.0 kg mass is connected to the end of string and moves about the string’s fixed end in a conical motion with a constant speed of 4.0 m/s. The string has a length of 2.50 m and forms an angle of theta with the vertical. What is the tension in the string?

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.

The next two questions share the same information Base your answers to questions 41 and 42 on the information and diagram below.

 A car and a truck are moving on a horizontal track. The position vs. time graph for the two vehicles is shown. 41. For the entire time shown in the graph, which one of the following choices correctly describes the relationship between the average speed of the truck to that of the car?

42. Which one of the following choices best describes the instants of time, t, at which the car and truck travel with the same speed?

43. An object of mass 4.0 kg has a total kinetic energy of 100.0 J and an x-component of linear momentum equal to 24.0 kg(m/s). The object is moving in the x-y plane. What is the y-component of the object’s linear momentum?
44. Which one of the following choices is most associated with the following statement: “When the pressure of a gas is held constant, the volume of the gas is directly proportional to the temperature.” ? 45. A 6.00 µF parallel-plate capacitor is disconnected from a 12 volt battery after being fully charged. A person now carefully inserts a dielectric material of constant κ = 2 so that it fills one-half of the space between the plates as shown. How much work was done by the person while inserting the dielectric? 46. A uniform rod of mass M and length L is fixed to rotate about a frictionless pivot located L/3 from one end. The rod is released from rest incrementally away from being perfectly vertical, resulting in the rod rotating clockwise about the pivot. When the rod is horizontal, what is the magnitude of the tangential acceleration of its center of mass?
47. One mole of a diatomic ideal gas undergoes a reversible adiabatic process. The pressure and volume initially are given as P = 2 atm and V = 30 L. If the volume is halved during the adiabatic process, how much work was done on the gas sample by the surroundings? 48. Two concentric charged conducting shells are in free space. The outer shell has inner radius 2a and outer radius 3a. The inner shell has radius a. It is known that the electric potential at If the electric potential Va at r = a is 0 volts, what is the charge on the inner spherical shell, Qin?
49. The kinetic energy associated with an electron is twice its rest energy. At what speed is the electron traveling? 50. A magnetic field directed into the plane of the page is decreasing in time. A constant is produced for the square loop enclosing the field in the figure. The square loop has three identical light bulbs of resistance R in it and an ideal voltmeter connected to the corners through the center of the loop. What is the magnitude of the voltmeter’s reading?

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