1997 Physics Quiz Bowl (21-40)

Questions 20, 21, and 22 refer to the motion of a toy car traveling along the x-axis. The graph shown below is a plot of the car’s velocity in the x direction, vx , versus time, t.

1997ques20diagram.gif (5496 bytes)

20. During what time interval was the car moving towards its initial position at constant velocity?

A. 0-10 s
B. 10-20 s
C. 20-25 s
D. 25-30 s
E. 30-35 s

21. What was the acceleration at 33 s?

A. + 0.40 m/s²
B. + 0.20 m/s²
C. 0 m/s²
D. - 0.20 m/s²
E. - 0.40 m/s²

22. How far did the car travel during the first 15 seconds?

A. 0
B 3.0 m
C. 15 m
D. 30 m
E. 45 m

24. The accompanying diagram shows the path that a light ray takes passing through three transparent materials. The indices of refraction in materials 1, 2, and 3 are n₁, n₂, and n₃, respectively. Which of the following best describes the relation between the indices of refraction?

1997ques24diagram.gif (1577 bytes)

A. n₁ > n₂ > n₃
B. n₁ > n₃ > n₂
C. n₂ > n₁ > n₃
D. n₂ > n₃ > n₁
E. n₃ > n₁ > n₂

25. Originally there are N atoms of an unstable isotope. After 20 minutes, only ¹/₁₆ of them have not decayed. What is the half life of the isotope?

A. 10 minutes
B. 5 minutes
C. 4 minutes
D. 2 minutes
E. 1 minute

26. The average speed of the atoms of a gas at 100 K is 200 m/s. What would most nearly be the average speed of the atoms at 300 K?

A. 67 m/s
B. 140 m/s
C. 200 m/s
D. 350 m/s
E. 600 m/s

27. Three resistors, R1 , R2 , and R3, are connected in series to a battery. Suppose R1 carries a current of 2.0 A, R2 has a resistance of 3.0 W, and R3 dissipates 6.0 W of power. What is the voltage across R3 ?

A. 1.0 V
B. 2.0 V
C. 3.0 V
D. 6.0 V
E. 12 V

28. An ion with charge q, mass m, and speed v enters a magnetic field B and is deflected into a path with a radius of curvature R. If a second ion has speed 2v, while m, q, and B are unchanged, what will be the radius of the second ion’s path?

A. 4R
B. 2R
C. R
D. ½ R
E. ¼ R

29. A student performs an experiment similar to Young’s Double Slit Experiment. Coherent light passes through two narrow slits and produces a pattern of alternating bright and dark lines on a screen. Which of the following would cause the bright lines on the screen to be further apart?

I. Increasing the distance between the slits.
II. Decreasing the distance between the slits.
III. Decreasing the wavelength of the light.

A. I only
B. II only
C. III only
D. I & III only
E. II & III only

30. A string with masses of 1.5 kg and 3.0 kg on its ends is hung over a frictionless, massless pulley as shown below.

1997ques30diagram.gif (1692 bytes)

What is the approximate magnitude of the acceleration of the masses?

A. 1.5 m/s²
B. 3.0 m/s²
C. 3.3 m/s²
D. 6.7 m/s²
E. 10 m/s²

31. Two blocks of mass 1.0 kg and 3.0 kg are connected by a string which has a tension of 2.0 N. A force F acts in the direction shown to the right. Assuming friction is negligible, what is the value of F?

A. 1.0 N
B. 2.0 N
C. 4.0 N
D. 6.0 N
E. 8.0 N

32. A wire moves through a magnetic field directed into the page. The wire experiences an induced charge separation as shown.

1997ques32diagram.gif (1302 bytes)

Which way is the wire moving?

A. to the right
B. to the left
C. out of the page
D. toward the top of the page
E. toward the bottom of the page

33. A softball player catches a ball of mass m, which is moving toward her with horizontal speed v. While bringing the ball to rest, her hand moves back a distance d. Assuming constant deceleration, the horizontal force exerted on the ball by her hand is

A. mv² / (2d)
B. mv² / d
C. mvd
D. 2mv / d
E. mv / d

34. Two large oppositely charged insulated plates have a uniform electric field between them. The distance between the plates is increased.

1997ques34diagram.gif (1117 bytes)

Which of the following statements is true?

I. The field strength decreases.
II. The field strength increases.
III. The potential difference between the plates increases.

A. I only
B. II only
C. III only
D. I and III only
E. II and III only

35. When a single resistor is connected to a battery, a total power P is dissipated in the circuit. How much total power is dissipated in a circuit if n identical resistors are connected in series using the same battery? Assume the internal resistance of the battery is zero.

A. n²P
B. nP
C. P
D. P/n
E. P/n²

36. A student performs the Photoelectric Effect Experiment and obtains the data depicted in the accompanying graph of E_km, the maximum kinetic energy of the photoelectrons in eV, versus f, the frequency of the photons in 10¹⁴ Hz.

1997ques36diagram.gif (3557 bytes)

What is the approximate work function for this material?

A. 1.5 eV
B. 2.0 eV
C. 2.7 eV
D. 4.0 eV
E. 6.0 eV

37. Consider the compound circuit shown to the right. The three bulbs 1, 2, and 3 – represented as resistors in the diagram – are identical.

1997ques37diagram.gif (1694 bytes)

Which of the following statements are true?

I. Bulb 3 is brighter than bulb 1 or 2.
II. Bulb 3 has more current passing through it than bulb 1 or 2.
III. Bulb 3 has a greater voltage drop across it than bulb 1 or 2.

A. I only
B. II only
C. I & II only
D. I & III only
E. I, II, & III

38. A vehicle traveling at a constant 0.60 c passes a clock at a street intersection. For a one-second interval on that clock, what interval will the driver of the vehicle measure?

A. 0.60 s
B. 0.80 s
C. 1 s
D. 1.25 s
E. 1.67 s

39. A cylinder free to turn around a fixed axis has a string wrapped around it as shown below. The string is pulled with a force F equal to the cylinders weight.

1997ques39diagram.gif (1154 bytes)

What is the acceleration of the string?

A. 2g
B. g
C. ½ g
D. ¼ g
E. F/g

40. A boat is traveling at 6.0 km/h 30º W of N with respect to a river. The river is flowing at 3.0 km/h from W to E. As observed from shore, the boat is traveling

A. 45º E of N
B. 30º E of N
C. due N
D. 30º W of N
E. 45º W of N