Write with all the steps and formulas and drawing if needed.​

The answer is not contained detail explanation, just a solution and the required values.

All the details are in the pictures, the answers are marked with orange colour.

Note,

in the task no 20.:

V - the velocity of the pair of the balls after collision.

in the task no 21:

m₁ - the mass of the copper ball; m₂ - the mass of the copper calorimeter; m₃ - the mass of the water; t₀ - the initial temperature of water in the copper calorimeter; θ - the final temperature in the calorimeter after the copper ball is transferred into a copper calorimeter; t₁ - the required initial temperature of the copper ball before it is transferred into the calorimeter.

the answer would be a