Find the area of semi circle and rectangle​

What are the three ways that an object can accelerate

Aphoton is absorbed by an electron that is in the n = 3 state of a hydrogen atom, causing the hydrogen atom to become ionized. very far away from the nucleus, the released electron has a velocity of 750,000 m/s. what was the wavelength of the absorbed photon?

Why does lightning travel from clouds to the ground?