An unknown solid material has a density of 50 lb/ft^3. If a one cubic foot piece

Question

An unknown solid material has a density of 50 lb/ft^3. If a one cubic foot piece of this material were placed in the Atlantic Ocean, it would: a) sink b)float c) it would definitely melt A cubic foot is a unit of: a) length b) area c) volume One gallon of gasoline weighs approximately 6.1 lbs How much does one liter of gasoline weigh? a) 1.6 lb b) 23.1 lb c) 12.2 lb Which of the following is commonly a source of "DC" voltage a) a wall outlet b) a battery c) an electric generator Coming out of a normal wall outlet is: a) 120 volts Dc b) 120 volts at 60 Hz c) 10 volts at 120 Hz Would a person normally hear a sound with a frequency of 10 MHz a) yes b) no c) it would depend on the amplitude Which of the following has the weakest magnetic field? a) the earth b) a magnet on your refrigerator door c) a MRI A pendulum has a period of 2.0 sec. How long will it take for ten cycles? a) 10 s b) 20 s c) 0.2 s Two identical aircraft engines are running. The total sound measured is 100 dB. If one of the engines were turned off, the sound level would now be: a) 103 dB b) 97 dB c) 50 dB The difference between de and dB (A) is: a) dB counts all frequencies equally and dB (A) does not b) dB are measured faster than dB (A)

Explanation / Answer

1)

density of ocean = 64.3 lb/ft^3

density of material < density of ocean

the solid floats

2)

volume

3)

1 gallon = 3.8 litres

1 litre = 1/(3.8) gallon

weight of 1 litre = 6.1/3.8 = 1.6 lb

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4)

a battry

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5)

option b

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6)

no

audibe range 20 Hz to 20000 Hz

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7)

the earth

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time = n*T = 10*2 = 20 s

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9)

100 = 10*log(2I/I0)

I0 = 10^-12

100 = 10*log(2I*10^12)

I = 0.005

intensity level = 10*log(0.005/10^-12) = 97 dB

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