An engineer claims to have measured the characteristics of a heat engine that takes in 150 J of thermal energy and produces 50 J of useful work. What is the smallest possible ratio of the temperatures (in kelvin) of the hot and cold reservoirs?

1.4999

Explanation:

Efficiency can be calculated using below expresion

Efficiency = W/Qeqn(1)

Where W= work = 50 J

Q= thermal energy= 150 J

But

W/Q= (Th-Tc)/Th Eqn(2)

Th= temperature of the hot

Tc= temperature of the cold

Where Th/ Tc= ratio of the temperature hot and cold reservoirs?

If we simplify eqn(2) we have

W/Q = 1-Tc/Theqn(3)

If we make the ratio subject of the formula we have

Tc/Th = 1-(W/Q)

Th/Tc = 1/(1-W/Q )

Then substitute the values

= 1/(1-50/150) = 1.4999

Hence, the smallest possible ratio of the temperatures (in kelvin) of the hot and cold reservoirs is 1.4999

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-nrel's geothermal analysts, scientists, and engineers perform a full range of research from developing advanced methods of locating and accessing geothermal resources to exploring innovative technologies to extract and produce clean energy from the heat of the earth

and here is the information for the technology of geothermal energy:

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-resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma

-almost everywhere, the shallow ground or upper 10 feet of the earth's surface maintains a nearly constant temperature between 50° and 60°f (10° and 16°c)

-geothermal heat pumps can tap into this resource to heat and cool buildings

-a geothermal heat pump system consists of a heat pump, an air delivery system (ductwork), and a heat exchanger-a system of pipes buried in the shallow ground near the building

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the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)