Html viewer was selected to open .htm files and that would not handle mailto: and other links. This app reset that and then next time I opened the file it asked what app to use and I could select Browser (or Chrome). Perfect. At times, I want to use Chrome to open an .html file that I put on my tablet.
Neutrons have a mass of 1.675 Ã 10-24g, which is a little heavier than the proton. Neutrons are 1839 times heavier than electrons. Like all hadrons, neutrons are made of quarks. A neutron is made of two down quarks and one up quark. One up quark has a charge of +2/3, and the two down quarks each have a charge of -1/3.
Assuming that the neutron mass was close to that of the proton, Chadwick bombarded hydrogen atoms with his produced neutrons to learn the speed of the protons after the collisions. Then setting the neutron speed equal to those proton speeds, he used the above energy expression to get a neutron mass of 938 +/- 1.8 MeV.