You said the answer in your question??
Answer:
Entropy:
Entropy is the measure of randomness of system.In other words the entropy is the measurement of tendency of system towards the disorder.
The concept of entropy arise from second law of thermodynamics.It is given as follows

Entropy is a extensive property of system .
Entropy of universe = Entropy of system + Entropy of surrounding.
The entropy of the system can be zero,positive and negative.But entropy of the surrounding can not be negative,but it can be zero or positive.
Actually the concept of entropy is difficult to understand because we can not visualize because it is not like beam and like rods.Only we have to realize that there is entropy.
Answer:
Given:
high temperature reservoir 
low temperature reservoir 
thermal efficiency 
The engines are said to operate on Carnot cycle which is totally reversible.
To find the intermediate temperature between the two engines, The thermal efficiency of the first heat engine can be defined as

The thermal efficiency of second heat engine can be written as

The temperature of intermediate reservoir can be defined as

Answer:
The angle between the earth and the sun as seen from a planet is called phase angle.
Answer:
F₁ = 1500 N
F₂ = 750 N
= 500 N
Explanation:
Given :
Power transmission, P = 7.5 kW
= 7.5 x 1000 W
= 7500 W
Belt velocity, V = 10 m/s
F₁ = 2 F₂
Now we know from power transmission equation
P = ( F₁ - F₂ ) x V
7500 = ( F₁ - F₂ ) x 10
750 = F₁ - F₂
750 = 2 F₂ - F₂ ( ∵F₁ = 2 F₂ )
∴F₂ = 750 N
Now F₁ = 2 F₂
F₁ = 2 x F₂
F₁ = 2 x 750
F₁ = 1500 N , this is the maximum force.
Therefore we know,
= 3 x 
where
is centrifugal force
=
/ 3
= 1500 / 3
= 500 N