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Sample MCAT Questions: Physical SciencesDIRECTIONS:
The following questions or incomplete statements are in groups. Preceding each series of questions or statements is a paragraph or a short explanatory statement, a formula or set of formulas, or a definition. Read the written material and then answer the questions or complete the statements. Select the ONE BEST ANSWER for each question and indicate your selectionby marking the corresponding letter of your choice on the Answer Form. Eliminate those alternatives you know to be incorrect and then select an answer from among the remaining alternatives. You may consult a periodic table if needed.
Passage I (Questions 31-36) A human centrifuge is used to test and train pilots and astronauts to withstand the large "g-forces" experienced during flight. The centrifuge arm length is such that the subject moves in a large circle of radius 9 m. The maximum angular velocity is 4 radians/sec. The subject normally faces inward toward the center of the circular path. ("eyeballs in"). During a test, the subject's respiratory and metabolic rate rise. The energy released per liter of oxygen consumed in human metabolism averages about 20,000 J/L.
31. What is the maximum linear (tangential) speed of the subject along the circular path at the maximum angular velocity of 4 radians/s?
A. 18 rn/sec C. 36 m/sec
32. A pilot of mass 82 kg (180 lbs) experiences 8 "g's" during one test for a period of 2 minutes. What is centripetal force, innewtons, acting on the pilot? A. 16N C. 960N B. 660N D. 6400N
33. In the earth frame of reference, what centrifugalforce acts on the pilot during the test? A. The centrifugal force on the pilot is equal and opposite the centripetal force on the pilot. B. The centrifugal force on the pilot is 1 "g" larger than the centripetal force on the pilot. C. The centrifugal force on the pilot is 1 "g" smaller than the centripetal force on the pilot. D. There is no centrifugal force on the pilot 34. The pilot's metabolic rate rises to 450 W and remains at that level during the 2 minute test period. What is the approximate number of liters of oxygen consumed by the pilot during the test period? A. 3L C. 6L B. 4L D. l0 L 35. What force acts on the back of the pilot's seat? A. 0 N C. 960N B. 88N D. 6400 N
36. The pilot now faces outward ("eyeballs out"). What effect does this have on the centripetal force acting on the pilot? B. The seat back now exerts an outward force. C. The centripetal force is replaced by the centrifugal force (now supplied by the pilot's seat harness). D. The centripetal force is unchanged (now supplied by the pilot's seat harness).
A brewery builds a cylindrical tank with 12 large electrical resistance heaters for the purpose of boiling city water to obtain distilled water. Each heater has a resistance of 15 ohms and normally draws a 20 Acurrent. The tank radius is 1.1 m and the normal depth of water will be 2.0m. An access hatch of 30 cm radius is designed to withstand a maximum gaugepressure of 31,000 N/rn2. When the tank is full the water pressureon the tank bottom is normally 19,500 N/rn2 when the tank is opento the air at I atm (1 atm = 1.01 x 105 Nim2). The tank can bepressurized so that the water will boil at a higher temperature than I 000 C. 37. The tank is filled to the normal 2 m depth and then pressurized
so that the maximum gauge pressure of 31,000 N/rn2 is exerted
on the tank bottom. Of this maximum pressure, how much is dueto
pressurization? B. 8200N/m2 D. 11,400 N/rn2
B 72,000W D. 52,000 W 39. What is the normal water volume in the cylindrical tank? B. 4.2 m3 D. 14.1 m3 40. The water enters the tank at 500C and boils at 1050C due to pressurization. If the current is increased until the 12 heaters are supplying 110,000 watts, how long will it take 5 m 3 (mass = 5,000 kg) of water to heat through the 55 0C rise? The heat needed to change the temperature of 1 kg of water by 10 C is its "specific heat" (c = 4190 joules/kg 0C).
A. 1.5 hours C. 2.9 hours B. 3.4 hours D. 6.2 hours 41. The tank can be filled to the normal 2 m depth (and volume) in 13 minutes by a pipe through which the fill water flows at a speed of 1.0 rn/sec. What is the cross-sectional area of the cylindrical fill pipe? A. 1.1m2 C. 0.05 m2
Question 42-48 are independent of any passage and of each other.
42. Small spheres of aluminum and lead, both of radius 2.0 cm, are suspended from strings and lowered into a container of waterof density 1000 kg/rn3. The density of aluminum is 2700 kg/rn 3 and of lead, 11,300 kg/rn3. The buoyant forces exerted on aluminum and lead are, respectively: B. 0.5 N and 0.2 N C. 0.33 N and 0.33 N D. 0.33 N and 0.2 N A. 12 rn/sec C. 21 rn/sec B. 72m/sec D. 144m/sec
44. A 6 cm tall object is 20 cm in front of a converging lens of focal length f = +10cm. Find the height of the image and state whether it is a real or virtual image. B. 12 cm tall, virtual image C. 12 cm tall, real image
B. T decreases by 50%. C. T increases by 50%.
A. 12 watts C. 60 watts B. 3 watts D. 24 watts
47. A spring compressed between 2 carts of unequal masses is released by burning a string and gives the 2-cart system a total kinetic energy KT = K1 + K2, where K1 and K 2 are the individual kinetic energies of the carts. Suppose m1 = 2m2; how do the values of K1 and K2 compare? A. K2=K1 C. K2 =K1/4 B. K2=K1 /2I D. K2=2K1
48. A constant force of 8 N acts on a 2 kg mass on a rough surface and a friction force of 4 N opposes the motion. If the mass has an initial velocity of 3 rn/sec, how far will the mass slide in 3 sec? A.18m C. 12m B. 36m D. 32m
Passage III (Questions 49-53) A solution of AgNO3 (1 x 10-6 molar) is prepared. To this is added K2CrO4 until precipitation of Ag2CrO4 begins. The Ksp of Ag2 CrO4 is 9 X 10-12.
49. The precipitate begins at a K2CrO4 concentration of about: A. 1 x 10-6. C. 1 x 10-1. B. 1 x l0-3. D. 1 x 101.
50. Addition of NaCl will bring about: C. precipitation of AgCl only if its Ksp is exceeded. D. A and C.
A.. bring about more complete precipitation. B. change the Ksp D. not be easily accomplished until ongoing precipitation is complete.
B. NaCl C. NaI D. all about the same (within a factor of 10)
B. precipitation of part of each of the three silver halides C. precipitation of' a portion of the two least soluble silver halides.
Many metals react with oxygen to form oxides. Some ofthese oxides, such as Na2O, CaO, and SrO, react with water toform basic solutions. (These oxides are called basic oxides or basic anhydrides.) Many nonmetals can react with oxygen to form oxides as well. These nonmetal oxides, however, react with water to form acidic solutions. Thus they are called acid anhydrides. 54. Phosphorus would be expected to react with oxygento form an oxide that will: B. react with water to form a basic solution.
55. Nitrogen will react with oxygen to form an oxide (N 205) that will: B. react with water to form a basic solution. C. react with water to form a neutral solution.
B. one mole of base in solution.
B. one mole of NaOH C. two moles of HCl
B. carbon dioxide. C. carbon monoxide.
Colligative properties of solutions are those proper- ties that depend on the concentration of molecules or ions in solution rather than on their identities.
60. Calculations of freezing point depression resulting from solutes are based on: A. molarity C. mole fraction.
B. freezing point depression. C. osmotic pressure.
B. lower the freezing point to-8 0C. C. produce a freezing point of 00C.
B. highest melting point. C. lowest molecular weight. |
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