Ablock of metal initially at 25°c is submerged in water initially at 75°c in a coffee cup. which of the following is true?
a. the final temperature of the coffee cup will be less than 20°c.
b. the final temperature of the coffee cup will be higher than 25°c but less than 75°c.
c. the final temperature of the coffee cup will be more than 80°c.
d. the final temperature of the coffee cup will be 80°c.

b. The final temperature of the coffee cup will be higher than 25°C but less than 75°C.

Explanation:

We know in thermal equilibrium.

Heat loss by one object = Heat gain by other object.

Now, heat is loss by the object whose temperature is higher than other because heat travels from high temperature to other.

And the object who gain heat its temperature increases till both body reach same temperature.

In this case, water loss heat, therefore its temperature decreases.

Similarly , metal block is at low temperature so its temperature increases.

Therefore , both water and metal block must have temperature less than and to have thermal equilibrium.  

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