text: if you get hit by a hailstone why doesn't it cause serious injury? if a penny falls from the sky and hits someone, it'd probably kill them, and yet a hailstone doesn't even though it's solid ice. why? hailstones do cause injury if they're large enough.  smaller ones are less harmful.  the reason lies in the density and air resistance difference between a penny and a hailstone.  a penny weighs about 3 grams.  a comparable hailstone would have to be at least .75 inches in diameter to be comparable in mass, and will have more wind resistance as it falls.    check out this link regarding hailstone injury