Biology Forums - Study Force

Carbon has a negative temperature coefficient of resistance of 0.5  103 (C)-1 . What temperature increase would result in a resistance decrease of 3 for a carbon resistor?
 a. 60C
  c. 20C
  b. 100C
  d. 40C

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[Ques. 2] A 15,000-N car on a hydraulic lift rests on a cylinder with a piston of radius 0.20 m. If a connecting cylinder with a piston of 0.050-m radius is driven by compressed air, what force must be applied to this smaller piston in order to lift the car?
 a. 600 N
  c. 3000 N
  b. 940 N
  d. 15,000 N

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[Ques. 3] The resistance of a platinum wire is to be calibrated for low-temperature work. A platinum wire with resistance 2.000 W at 20C is immersed in liquid nitrogen at 77 K (-196C). If the temperature response of the platinum wire is linear, what is the expected resistance of the platinum wire at -196C? aplatinum = 3.92  10-3 (C)-1.
 a. 0.153 W
  c. 3.69 W
  b. 1.768 W
  d. 0.307 W

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[Ques. 4] How deep under the surface of a lake would the pressure be triple that at the surface? (1 atm = 1.01  105 Pa)
 a. 1.00 m
  c. 10.3 m
  b. 9.80 m
  d. 20.6 m

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[Ques. 5] A tungsten wire is used to determine the melting point of indium. The resistance of the tungsten wire is 6.000 W at 20C and increases to 9.700 W as the indium starts to melt. atungsten = 4.50  10-3 (C)-1 . What is the melting temperature of indium?
 a. 351C
  c. 132C
  b. 731C
  d. 157C

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[Ques. 6] The water behind Grand Coulee Dam is 1200 m wide and 160 m deep. Find the hydrostatic force on the back of the dam. (Hint: the total force = average pressure  area)
 a. 5.2  109 N
  c. 13.2  1010 N
  b. 8.8  1010 N
  d. 15.1  1010 N

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[Ques. 7] A certain material is in a room at 27C. If the absolute temperature (K) of the material is tripled, its resistance quadruples. (Water freezes at 273 K.) What is the value for a, the temperature coefficient of resistivity?
 a. 0.0050 (C)-1
  c. 1 (C)-1
  b. 0.0025 (C)-1
  d. 3 (C)-1

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[Ques. 8] Atmospheric pressure is 1.0  105 N/m2, and the density of air is 1.29 kg/m3 . If the density of air is constant as you get higher and higher, calculate the height of the atmosphere needed to produce this pressure.
 a. 7900 m
  c. 1260 m
  b. 77,000 m
  d. 10,300 m

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[Ques. 9] A metal wire has a resistance of 10.00 W at a temperature of 20.0C. If the same wire has a resistance of 10.55 W at 90C, what is the resistance when its temperature is 0.0C?
 a. 13.8 W
  c. 9.84 W
  b. 9.69 W
  d. 0.70 W

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[Ques. 10] Dams at two different locations are needed to form a lake. When the lake is filled, the water level will be at the top of both dams. Dam 2 is twice as high and three as wide as Dam 1 . How much greater is the force of the water on Dam 2 than the force on Dam 1? (Ignore atmospheric pressure; it is pushing on both sides of the dams.)
 a. 24
  c. 6
  b. 12
  d. 3

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Were some really tough homework problems!