 AAPT Quiz 2000 Physics Olympiad Screening Test (Part 2)
21. A converging lens has a focal length of 10 cm. If an object is placed 50 cm from the lens, what will be the magnitude of the magnification of the image?
22. Viewed from one frame of reference, a 1500 kg automobile with a velocity of 25 m/s collides with a 1000 kg automobile at rest. The two automobiles stick together. What would be the velocity of the two cars immediately after the collision in a frame of reference moving at 10 rn/s in the same direction as the 1500 kg automobile?
23. The most common isotope of Uranium, 238 92U, radioactively decays into 206 82Pb, Lead, by means of a series of alpha and beta particle emissions. How many of each particle must be emitted?

24. A small bird with a mass of 0.5 kg takes off from the ground and flies with an upward velocity of 3 m/sec for 10 seconds. Which of the following is closest to the minimum power that must be developed by the bird?
25. Two iron spheres separated by some distance have a minute gravitational attraction, F. If the spheres are moved to one half their original separation and allowed to rust so that the mass of each sphere increases 41%, what would be the resulting gravitational force?
26. After the switch in the accompanying circuit has been closed for a very long time, what would be the total current in the circuit shown below? 27. Which of the following graphs would best represent the resistance versus temperature relationship for a superconductor?

28. A moving charged particle experiences no magnetic force. Which of the following statements MUST be true?

Questions 29 and 30 refer to the following situation.

Three electric charges (Q1, Q2 and Q3) are arranged at three corners of a rectangle as shown in the diagram and each has a charge of -40 nC. 29. What is the magnitude of the net force on Q2?
30. What would be the magnitude of the total electric field at center point X?