# Search results

1. ### Kinetic energy change with initial velocity

It is my understanding that to calculate the change of kinetic energy of an object that speeds up from vi to vf you use this formula: Change of kinetic energy = 1/2 * m * (vf2 - vi2) When the initial velocity is 0 m/s I have no problems, but let's say an object that weighs 2 kg speeds up from...
2. ### Does water slow light down?

I know that light slows down once it crosses the border between air and water. But once the light is in water, is its speed constant or does it slow down, much like a person, who has jumped into water from a good height, penetrates water slower and slower due to water resistance?
3. ### Two balls dropped from the same height

I have seen youtube videos where two balls of the same size and of different masses are dropped from the same height and they hit the ground at the same time. I understand why this is so: the increase in the mass of a body increases the force of gravity acting on the body, but also decreases...