-di represents an image in front of a lens
No, speed is not a vector. it is scalar.
because it doesn't need direction but need magnitude.
Is the velocity constant? Is there any friction?
3 meters per second
then after 40 seconds it must 3*40 = 120 meters
120 meters or 0.12 km if you will
Yeah, it's every state. Atoms need a certain quanta of energy to jump to each state of energy, and therefore change state depending on how much energy is absorbed and/or released. This applies to all states of matter.
