Suppose you are driving a car and your friend, who is with you in the car, tosses a softball up and down from her point of view.
A second friend of yours stands on the street and sees you passing by and says, "You are testing projectile motion with the softball!". Your friend on the street claims that each of you measures a different value for the vertical component of the initial velocity of the softball. Do you agree with the statement?
If the car is moving, it only has a velocity with a component in the horizontal direction. If we use galilean relativity, the velocity of the ball observed by my friend standing in the ground should only be affected in the horizonal direction, while the vertical stays the same for both observers.
The transfer of energy means, in convention process, transport of matter. In this case, hot water has lower density than cool water. The water with less density ascends and leaves gaps that are occupied with cooler water "packages".
