28. A long straight wire has a conventional current directed into the plane of the page as shown in the figure. Which one of the arrows shown best indicates the direction of the magnetic field associated with this wire at the location labeled P?

 

31. Three particles with charges Q, Q, and Q₂ and are initially at rest very (infinitely) far apart from one another. The particles are moved to the locations shown in the figure where they are fixed in place. The particles on the left and right have charge Q and are separated by a distance R. The particle with charge Q₂ is located at the midpoint directly between the other charged particles. The total work required to configure this three-particle arrangement is  0 J. Ignore any self-energies for the particles. What is the value of the charge Q₂?

 

 

33. A solid, uniform sphere rolls without slipping on a floor along the +x-axis (to the right). The rotational kinetic energy associated with the sphere about an axis of rotation through its center of mass along the +z-axis (out of the plane of the page) is 20 J. What is the translational kinetic energy associated with the sphere?

 

34. A mass m attached to a light string of length L is located at an angle below the horizontal as shown in the figure to the left. The mass then is released from rest. Calculated from an axis perpendicular to the plane of the page through the pivot, which one of the following choice represents the magnitude of the torque produced by the gravitational force acting on the mass at this instant?

36. A positive charge moves with constant velocity through a region of space containing both an electric field and a magnetic field. The electric field is directed out of the plane of the page. Ignoring any gravitational field, which one of the following choices represents possible directions of both the particle’s velocity and the total magnetic field in the region of space?

 

 

38. A square, conducting wire loop sits in a plane perpendicular to a spatially uniform magnetic field pointing into the plane of the page as shown. The magnetic field strength steadily increases with time. Which one of the following effects best describes the result of this field increase?

 

39. For the circuit shown, all wires have no resistance, the battery has a constant internal resistance of  r = 8.0 ohms and the two light bulbs (#1 and #2) are identical, each with resistance R_bulb. The variable resistor is initially set to 26.0 ohms. The switch S in the circuit now is closed. To what resistance must the variable resistor be set if bulb #1 is to have the same brightness after the switch is closed as it did with the switch open?

 

44. A monatomic ideal gas is the working substance for a refrigerator that undergoes the cyclic process (ABCDA) shown in the PV diagram. The processes are all isochoric or isobaric with pressures between P_o and 2P_o and volumes between V_o and 2V_o. What is the coefficient of performance for this refrigerator?

46. There is a quantity called the Planck time, t_Planck, which is computed in terms of constants as is Planck’s constant divided by , G is the Universal Gravitational Constant, and c is the speed of light. In order for this expression for time to be consistent, what is the numerical value of n, the power to which the speed of light is raised?

47. Water flows ideally through a cylindrically-shaped pipe. At the lower end, the pipe’s cross-sectional area is 30.0 cm² whereas in the upper portion, the pipe’s cross-sectional area is 10 cm² and fluid is moving at 9.0 m/s. Which one of the following choices best represents the difference in pressure between the lower section of the pipe and the upper section if the vertical distance between the centers of the pipe sections is 2.0 m?

48. An object of mass M is dropped from a height H above the ground. The object bounces off of a horizontal surface in a collision lasting time T. The object then rises upward to a maximum height H/2. What was the magnitude of the average net force acting on the mass during the collision with the surface?

49. A beam of unpolarized light traveling in air strikes a piece of optically flat glass at an angle of incidence of 58º. Some of the light is reflected while the remainder is transmitted into the glass. The reflected beam is 100% polarized parallel to the surface of the glass. What is the index of refraction for the glass?

 

 

50. A spatially uniform electric field is constrained within the circular region of radius R as shown. The field is directed out of the plane of the page and its strength is decreasing uniformly with time. Which one of the following choices best represents the direction of the Lorentz force on the electron at the instant shown in the figure when the electron is moving up the plane of the page? Ignore gravity.