Saving Lives

New medical students were made to take an extremely difficult class in physics.
One day the lecturer was discussing a particularly difficult concept.
A student rudely interrupted to ask, “Why do we need to learn this stuff?”
“To save lives,” the lecturer responded quickly and continued.
A few minutes later, the same student spoke up again. “So how does physics save lives?” he persisted.
“It keeps idiots like you from graduating,” replied the lecturer.