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Novay_Z [31]
3 years ago
14

(a) What is the best coefficient of performance for a refrigerator that cools an environment at −30.0ºC and has heat transfer to

another environment at 45.0ºC ? (b) How much work in joules must be done for a heat transfer of 4186 kJ from the cold environment? (c) What is the cost of doing this if the work costs 10.0 cents per 3.60×106J (a kilowatt-hour)?
Physics
1 answer:
kari74 [83]3 years ago
4 0

Answer:

a) 3.242

b) 1291.178 KJ

c) 3.59 cents

Explanation:

a) First all the temperature units should be in Kelvin. -30°C + 273.15 = 243.15K and 45°C + 273.15 = 318.15K. Coefficient of performance for refrigerator is COP = TL/(TH-TL) where TL is Lower Temperature and TH is the Higher Temperature. COP = 243.15/(318.15-243.15) = 3.242

b) COP  = Cooling Effect/Work Input. Cooling Effect (or Desired Output) is 4186 kJ.

So Work Input = Cooling Effect/COP = 4186KJ/3.242= 1291.178 KJ

c) 3.6 MJ (3600kJ) is for 10 cents, using ratio for cost: energy used

\frac{10}{3600 kJ} =\frac{x}{1291.178kJ}

3.59 cents

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While traveling along a highway a driver slows from 31 m/s to 15 m/s in 8 seconds. What is the automobile’s acceleration? (Remem
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Answer:

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Explanation:

The acceleration is defined as the rate of change of the velocity.

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In this case, we have:

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How can a 1kg ball have more kinetic energy than a 100kg ball? Explain both using words and by providing a numerical example
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1 kg ball can have more kinetic energy than a 100 kg ball as increase in velocity is having greater impact on K.E than increase in mass.

<u>Explanation</u>:

We know kinetic energy can be judged or calculated by two parameters only which is mass and velocity. As kinetic energy is directly proportional to the (velocity)^2 and increase in velocity leads to greater effect on translational Kinetic Energy. Here formula of Kinetic Energy suggests that doubling the mass will double its K.E but doubling velocity will quadruple its velocity:

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It shows that man A will have more K.E.

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