Answer : The temperature of the hot reservoir (in Kelvins) is 1128.18 K
Explanation :
Efficiency of carnot heat engine : It is the ratio of work done by the system to the system to the amount of heat transferred to the system at the higher temperature.
Formula used for efficiency of the heat engine.
where,
= efficiency = 0.780
= Temperature of hot reservoir = ?
= Temperature of cold reservoir = 
Now put all the given values in the above expression, we get:
Therefore, the temperature of the hot reservoir (in Kelvins) is 1128.18 K
Explanation:
Below is an attachment containing the solution to the question.
Radial acceleration is = v^2/r
Therefore (8.8m/s)^2/(25m)= 3.10m/s^2
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The refractive index or index of refraction of a medium is the ratio of speed of light in vacuum to that in the medium. It is measured by, 
. 'n' is the refractive index, c is the speed of light in the vacuum and v is the speed of light in the medium. So, the light would travel the slowest in the medium of highest refractive index. Diamond is known to have highest refractive index among the all the natural material. Its refractive index is 2.4175.
