Only one color, but not one size, Stuck at the bottom, yet easily flies.
Present in sun, but not in rain,
Doing no harm, and feeling no pain.
What is it?
Let's see who's the smartest :) ❕❕❕❕

your answer is SHADOW

A shadow

Explanation:

It is stuck at the bottom because if it always below you, but it flies because it travels at the same speed as light, the sun is what creates it, and you need the sun to have one.

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.