# Momentum and Impulse Examples

Momentum and Impulse
An object has a momentum if it has a velocity. Momentum is calculated by multiplying the mass and velocity together. Impulse is directly related to momentum because impulse is a term describing an object's change in momentum. In other words, if an object changes speed, then its momentum changes. By definition this measurable quantity of momentum changing is the impulse of the object. In order for an object's momentum to change, a force must be applied for a period of time. So the change in momentum, or impulse, also referred to as ∆p can be calculated by multiplying the force by the time the force is exerted, F x t. If a large force is exerted over a small period of time, a large change in momentum can occur. If a small force is applied over a long period of time, the change in momentum can also be large. The force exerted over the time period causes a change in the object's velocity which causes the momentum to change. If the force is exerted in the opposite direction of the object's original momentum, the object's momentum will decrease. If the force is exerted in the same direction as the object's original velocity, then the momentum will increase. If an object is at rest and does not have any momentum then a force large enough to overcome friction will cause the object to move giving the object some momentum.
Examples of Momentum and Impulse:

1. In baseball, a ball that is only struck with a small part of the bat is not in contact with the bat for a long period of time so the change in momentum, or impulse, is small and the ball does not travel very far. However, if the bat strikes the ball squarely, the force is exerted for a longer time resulting in a greater change in momentum, or greater impulse, and the ball travels very far.

2. Air bags in cars are designed with impulse, or momentum change principles. When a driver gets into an accident their momentum carries them forward into the steering wheel. By putting an airbag in the car, a smaller force is exerted over a longer period of time to change the momentum of the driver to a stop. Without the airbag, a large force is exerted over a short time causing more damage to the driver.

3. A car traveling down the road is slowed down slightly when the brakes are just gently tapped. The force of the brakes is exerted over a small time resulting in a small impulse and a small change in the momentum of the car.

4. If you have ever competed in an egg toss competition and done well, you were putting impulse into action. In order to reduce the amount of force on the egg so it doesn't break when you catch it, you move your hands in the same direction as the egg as you catch it. This action increases the amount of time you apply force on the egg and the amount of force acting on the egg to change its momentum is reduced so the egg will not break.

5. A golf ball sits on a tee motionless before the golfer swings the club and strikes the ball. If the ball is struck in the center of the club with a good follow-through, then force is exerted for a longer time resulting in a greater change in momentum, greater impulse, and the ball will travel farther. If the ball is not struck in the center or the club, then the amount of force is only enacted on the ball for a short time resulting in a smaller change in momentum and the ball doesn't go as far.

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