The Car Crash That Rewrote Physics Textbooks

In 1997 a 900 kg Volvo travelling 40 km/h collided head-on with a 2 000 kg truck doing the same speed in the opposite direction. Everyone expected the car to disintegrate. Instead, the truck bounced backwards. Why? Momentum conservation. Total momentum before the crash was zero - after it had to stay zero. The heavier truck reversed direction, while the lighter car kept going forward under the truck. Volvo used the wreck in ads for years.

Explosions Are Just Momentum in a Hurry

Fire a gun and the bullet races forward while the shooter feels a kick backward. Newton’s third law in action - the total momentum of bullet plus gun stays exactly zero after the powder burns. Same reason rockets work in space: hot gas shoots one way, spacecraft goes the other. No air needed.

  1. Sports Tricks That Only Work Because of Momentum
  2. Baseball batters step into the pitch to add body momentum to the swing
  3. Ice skaters pull arms in to spin faster while angular momentum stays constant
  4. Divers tuck tight then open to control rotation - again angular momentum conserved
  5. Table-tennis players put insane spin by brushing the ball sideways instead of hitting dead center

All free wins from the same conservation law.

The Weirdest Momentum Facts on Earth

  1. A supertanker at 10 knots carries as much momentum as a fully loaded Boeing 747 flying at takeoff speed
  2. Neutrinos have almost zero mass yet cross the planet with huge momentum because they travel near light speed
  3. When a .50 BMG bullet hits water, it stops in less than a meter - water molecules can’t move aside fast enough and absorb the momentum like a wall
  4. Olympic hammer throwers spin three times to pile up angular momentum before release - the 7.26 kg ball leaves their hand at over 100 km/h
  5. The Pioneer spacecraft are still coasting outward with the exact momentum they got from their last engine burn in the 1970s - no friction in space
  6. Fleas accelerate at 100 g when jumping - their legs store momentum in elastic resilin pads before release

Elastic vs Inelastic - Why Some Crashes Hurt More

Perfectly elastic collisions keep kinetic energy - billiard balls do it almost perfectly. Real car crashes are inelastic - kinetic energy turns into bent metal and heat, yet momentum is still perfectly conserved. That difference explains why crumple zones save lives - they stretch the collision time, so force stays survivable.

Need to Calculate Any Momentum Problem?

From asteroid impacts to hockey pucks - use Our Momentum Calculator. Drop in masses and velocities, choose elastic or inelastic, get final speeds and momentum change in one click.

The Deep Reason Momentum Never Lies

Einstein showed momentum conservation comes straight from the symmetry of space - if physics works the same here and a meter over, total momentum has to stay constant. Same for time symmetry giving energy conservation and rotation symmetry giving angular momentum. Three of the deepest laws in nature, all hidden inside something school kids learn in week one.

Next time something crashes, kicks, explodes or just coasts quietly through space - remember momentum is silently keeping score. A bullet, a planet or a flea - they all play by the exact same unbreakable rule.