Physics
Force and Motion
Quick fact
A spacecraft drifting in deep space can travel at constant velocity forever with no force acting on it—only a force (like a thruster) would alter its motion.
Why this is interesting
Have you ever wondered why a ball rolling across a floor eventually stops? Is it because it 'runs out' of force? The answer might surprise you: it's actually the opposite—forces are what cause motion to change, not to continue.