1996 Physics Quiz Bowl (21-40)

21. Two isolated conducting spheres (S₁ of radius 0.030 m and initial charge + 6.0 nC and S₂ of radius 0.040 m and initial charge + 2.0 nC) are connected by a conducting wire. Charge will flow in the wire until:

A. both spheres are equally charged.
B. the net charge is zero.
C. the force of repulsion between the two spheres becomes equal.
D. both spheres have the same surface charge density.
E. both spheres are at the same potential.

22. When an ideal gas is isothermally compressed:

A. thermal energy flows from the gas to the surroundings.
B. the temperature of the gas decreases.
C. no thermal energy enters or leaves the gas.
D. the temperature of the gas increases.
E. thermal energy flows from the surroundings to the gas.

23. A hypothetical planet has seven times the mass of Earth and twice the radius of Earth. The magnitude of the gravitational acceleration at the surface of this planet is most nearly:

A. 2.9 m/s²
B. 5.7 m/s²
C. 17.5 m/s²
D. 35 m/s²
E. 122 m/s²

24. A 2.0-kg ball is attached to a 0.80 m string and whirled in a horizontal circle at a constant speed of 6.0 m/s. See figure to the right. The work done on the ball during each revolution is:

A. 450 J
B. 90 J
C. 72 J
D. 16 J
E. zero

25. Which of the following is NOT possible for the images formed by the lens in the accompanying figure?

A. real and inverted
B. real and smaller in size
C. real and larger in size
D. virtual and erect
E. virtual and smaller in size

26. If the speed of sound in air is 340 m/s, the length of the organ pipe, open at both ends, that can resonate at the fundamental frequency of 136 Hz, would be:

A. 0.625 m
B. 0.750 m
C. 1.25 m
D. 2.50 m
E. 3.75 m

27. A long straight wire conductor is placed below a compass. When the conventional current in the conductor is from south to north and large, the N pole of the compass:

1996ques27diagram.gif (1532 bytes)

A. remains undeflected.
B. points to the south.
C. points to the west.
D. points to the east.
E. has its polarity reversed.

28. A photon with frequency f behaves as if it had a mass equal to:

29. Two large parallel plates a distance d apart are charged by connecting them to a battery of potential difference V. The battery is disconnected, and the plates are slowly moved apart. As the distance between plates increases:

A. the charge on the plates decreases.
B. the electric field intensity between the plates increases.
C. the electric field intensity between the plates decreases.
D. the potential difference between the plates decreases.
E. the potential difference between the plates increases.

30. An 800-kg elevator accelerates downward at 2.0 m/s² . The force exerted by the cable on the elevator is:

A. 1.6 kN down
B. 1.6 kN up
C. 6.4 kN up
D. 8.0 kN down
E. 9.6 kN down

31. See the accompanying figure.

1996ques31diagram.gif (2216 bytes)

What is the current through the 300 W resistor when the capacitor is fully charged?

A. zero
B. 0.020 A
C. 0.025 A
D. 0.033 A
E. 0.100 A

32. The 10.0 kg box shown in the figure below is sliding to the right along the floor. A horizontal force of 10.0 N is being applied to the right. The coefficient of kinetic friction between the box and the floor is 0.20. The box is moving with:

1996ques32diagram.gif (1578 bytes)

A. acceleration to the left.
B. centripetal acceleration.
C. acceleration to the right.
D. constant speed and constant velocity.
E. constant speed but not constant velocity.

33. Two blocks X and Y are in contact on a horizontal frictionless surface. A 36 N constant force is applied to X as shown to the right. The force exerted by X on Y is:

1996ques33diagram.gif (1818 bytes)

A. 1.5 N
B. 6.0 N
C. 29 N
D. 30 N
E. 36 N

34. A point charge +q is placed midway between two point charges +3q and -q separated by a distance 2d. If Coulomb’s constant is k, the magnitude of the force on the charge +q is:

35. A projectile of mass m is fired horizontally from a spring gun that rests on a horizontal frictionless surface. See the accompanying figure. The mass of the gun is M . If the kinetic energy of the projectile after firing is E_k , the gun will recoil with a kinetic energy equal to:

36. An isolated conducting sphere of radius R has positive charge + Q. Which graph best depicts the electric field as a function of r, the distance from the center of the sphere?

1996ques36ans.gif (2948 bytes)

37. Four identical light bulbs K, L, M, and N are connected in the electrical circuit shown in the accompanying figure. Bulb M burns out. Which of the following statements is true?

1996ques37diagram.gif (1775 bytes)

A. All the light bulbs go out.
B. Only bulb M goes out.
C. Bulb N goes out but at least one other bulb remains lit.
D. The brightness of bulb N remains the same.
E. Bulb N becomes dimmer but does not go out.

38. A pendulum bob mass m on a cord length L is pulled sideways until the cord makes an angle q with the vertical as shown in the figure to the right. The change in potential energy of the bob during the displacement is:

1996ques38diagram.gif (1252 bytes)

A. mgL (1 – cosq)
B. mgL (1 – sinq)
C. mgL sinq
D. mgL cosq
E. 2mgL (1 – sinq)

39. Assume the objects in the following diagrams have equal mass and the strings holding them in place are identical. In which case would the string be most likely to break?

1996ques39ans.gif (3144 bytes)

40. A proton of mass M and kinetic energy E_k passes undeflected through a region with electric and magnetic fields perpendicular to each other. The electric field has magnitude E. The magnitude of the magnetic field B is: