Acarnot engine has an efficiency of 23.9%. it operates between constant-temperature reservoirs differing in temperature by 68.8°c. in kelvins, what are (a) the temperature of the hot reservoir and (b) the temperature of the cold reservoir?

(a) 287.9 K

The efficiency of the engine is given by

where

Tc is the temperature of the cold reservoir

Th is the temperature of the hot reservoir

We can rewrite the two temperatures as

(because differences in Kelvin are equal to differences in Celsius)

So we can rewrite the 1st equation as

We also know the efficiency:

So we can re-arrange the previous equation to find the temperature of the hot reservoir:

(b) 219.1 K

The temperature of the cold reservoir can be found as:

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.

80cm/s.

24cm/s.

53.3cm/s.