The young professor vik.

Thanks a lot. Didn't think of that!

1 calorie is approximately 4.184joules. Energy and temperature are related thermodynamically. Read the topic of thermodynamics in your textbook for explanation. Water has a latent(hidden) heat of vaporization of 2260joules. Since 1 calorie = 4.184joules; from simple proportion 2260 would be 2260/4.184 = 565 calories. This value is close to what is in your textbook. The value in your textbook might have been gotten experimentally. An as you know error cannot be avoided in experiments. Hence an error (probably impurities in water or cheer carelessness) in the experiment might be responsible for the increase in the value (580cals). This increase has nothing at all to do with hydrogen bonding. 1 calorie is approximately 4.184joules. Energy and temperature are related thermodynamically. Read the topic of thermodynamics in your textbook for explanation. Water has a latent(hidden) heat of vaporization of 2260joules. Since 1 calorie = 4.184joules; from simple proportion 2260 would be 2260/4.184 = 565 calories. This value is close to what is in your textbook. The value in your textbook might have been gotten experimentally. An as you know error cannot be avoided in experiments. Hence an error (probably impurities in water or cheer carelessness) in the experiment might be responsible for the increase in the value (580cals). This increase has nothing at all to do with hydrogen bonding. Reply if this helps or for further questions!

Gravity is independent of height. Hence it cancels out.

Applying the theory, that the centripetal force pulling the body toward the centre equals the force due to gravity. You should use the formula; mv^2/r =mg. You can calculate v which is your velocity.