sentences:  In 1903, Hopkinson was elected to the Cambridge chair in mechanism and applied mechanics, and in 1910 he was elected a Fellow of the Royal Society.During World War I he was commissioned into the Royal Engineers, and opened a research establishment at Orford Ness where he and his team researched weapons, sights, and ammunition.In 1915, Hopkinson discovered a similarity relation between the masses of explosive charges and their effects at a given distance.