If you are not ready, and did not know what to do, it could hurt you in different ways. It could knock you down, hard, or throw you against a tree or a wall. It is such a big explosion, it can smash in buildings and knock signboards over, and break windows all over town, but if you duck and cover, like Burt [the Turtle], you will be much safer.
From Duck and Cover (1951), about protecting yourself from an atomic explosion.
