Why do you use rulers in science ?

An electron moved from shell n = 2 to shell n = 1. what most likely happened during the transition? a fraction of a photon was added. a photon of energy was absorbed. a fraction of a photon was removed. a photon of energy was released.

The molar mass of nickel(ni) is 58.7 g/mol. how many moles are in an 88 gram sample of nickel?

Aseismic wave is energy released as the result of rock movement along a fault. t or f ?