What did scientists believe flipped in the past

The protons of bromomethane(ha) and flouromethane(hb) are subjected to an external magnetic field of 100mhz. which proton will experience higher external magnetic field and why?

Atest tube is filled with water and end closed. it contains a small steel ball and an air bubble. the test tube is rotated in a horizontal circle, with the of string then 1. both steel ball and air bubble move outwards 2. both steel ball and air bubble move inwards 3. steel ball move outwards and air bubble moves inwards 4.steel ball moves inwards and air bubble moves outwards

Prove that relative velocity of approach before collision is equal to relative velocity of seperation after elastic collision.