Chapter 2, Section 3 Momentum Notes
Momentum, Mass and Velocity
Momentum is a quantity defined as the product of the mass and velocity of an object
The more momentum an object has, the harder it is to stop that object or change its direction. Example: If you were trying to stop a car a bike vs a car, it would be easier to stop the bike than the car because the car has more momentum due to its greater mass. A larger force would be needed to stop the car.
An object with greater speed/velocity will also have a greater momentum and will be harder to stop. If two cars of the same mass were traveling, it would be easier to stop the one that has less speed than the one with greater speed.
Calculating Momentum
To calculate momentum, we use the equation P= m x v P=momentum m=mass v=velocity units are kg x m/s (+ direction) files/momentum.swf
The Law of Conservation of Momentum
When one object hits another object, some or all of the momentum of the first object will be transferred to the object that is hit. Example: when a car is in an accident the momentum of the first car gets transferred to the second car.
The Law of Conservation of momentum states that any time objects collide, the amount of momentum stays the same.
The momentum will stay the same for collisions if no other forces act on the colliding objects.
The law of conservation of momentum applies to objects whether they stick together or bounce off one another.
Objects that Stick Together
If objects stick together during a collision, they will act as one object after the collision.
The mass of the combined objects is equal to the masses of the two objects added together Example: if one person tackles another, the mass of the two people will be equal to their combined masses.
If there is a head on collision, the objects will move in the direction of the object that had the greater momentum before the collision. Example: If a truck hit a car, and both vehicles were going the same speed, they will move in the direction that the truck was originally going because it had a greater momentum than the car.
The velocity of the objects sticking together will be different than the original velocity of the objects before the collision.
Objects that Bounce Off Each Other
When an object bounces off another object, the momentum from the first object is usually transferred to the second object. Example: bumper cars, billiard balls, a bowling ball & pins
The transfer of momentum causes objects to move in different directions at different speeds. The total momentum of the objects will remain the same as before the collision.
Conservation of Momentum and Newton’s Third Law
Newton’s third law states that for every action there is an equal and opposite reaction. This occurs in the law of conservation of momentum as well. Example: If a cue ball hits a billiard ball. The cue ball hitting is the action force, the reaction force is the billiard ball applying force back onto the cue ball.