What makes a planet different from other celestial bodies? SIMPLE WORDS>

Asimply means that over time there was some sort of change.

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

What type of light does this light bulb produce most (i.e. at what wavelength does the spectrum have maximum intensity)?