All About Momentum and Collisions

Momentum and Collisions


Momentum is a measurement of mass in motion. The momentum of an object in motion equals its mass times its velocity. A collision happens when two moving objects hit into each other. The intensity of the collision is connected to the momentum of the objects.


Fun Facts

  • In order for an object to have momentum, it has to have a force acting on it. A ball can be kicked, a car has the force of the engine moving it. A force is anything that changes how an object moves.
  • Momentum is abbreviated using the letter “p”. Since momentum equals mass times velocity, the equation looks like this: p = mv.
  • Momentum is a combination of mass and velocity, so they both have equal impact on the amount of momentum. If mass and velocity are both great the momentum will also be great. If the mass is large but the velocity is small, like a bulldozer moving slowly, the momentum will be small. If the mass is small but the velocity is great, like an engine firing a model rocket, the momentum will be great.
  • The intensity of a collision has to do with the momentum of both objects. If two cars collide when moving slowly, even though they have large mass, the damage would be minimal.
  • Many collisions are intentional, like a baseball bat hitting a baseball. We often think of collisions as accidental like when two cars hit into each other or two people run into each other.
  • When two objects collide the total momentum before the collision is equal to the total momentum after the collision. If an object moving fast hits into an object moving slowly the object that was moving fast slows down and the one moving slowly speeds up. The mass of the objects naturally affects the outcome of a collision.
  • Energy is transferred during a collision. Think of a baseball being hit by a baseball bat. At the moment of collision the force from the person swinging the bat causes the velocity of the ball to increase and the direction to change.
  • The amount of energy transferred during a collision depends on the mass and velocity of the objects.



Mass: The measure of the amount of matter in an object. It is not the same as the weight of an object, because weight is affected by gravity.

Velocity: The rate and direction of the movement of an object. It is not the same as speed, because speed doesn’t include direction.


Questions and Answers

Question: Do automobile designers consider what will happen in a collision?

Answer: Yes, automobile designers know that a vehicle will be deformed when involved in a collision, so they design it in a way that will be most safe for the passengers.


Watch a video to learn more about collisions.