Momentum

Momentum is a property of an object in motion, whether it is a person, car, truck, or space ship. A car traveling down the road has momentum; it requires force from the brakes to change its velocity. A big truck traveling at the same velocity has much more momentum, because it is more difficult to change its velocity. Momentum is a quantity that describes the tendency for an object in motion to remain in motion.
The momentum of a moving object is its mass multiplied by its velocity. The higher an object's mass or velocity, the more momentum it has. A truck has more momentum than a car moving at the same speed because the truck has more mass. Similarly, a car has more momentum when it is moving fast on the highway than when it is traveling slowly on a city street.
(2.12) p =m v
p  = momentum (kg m/s)
m  = mass (kg)
v  = velocity (m/s)
Momentum
vector notation
Momentum is the product of mass and velocity; since velocity is a vector quantity, momentum is therefore also a vector quantity. Momentum in one dimension can take on either positive or negative signs to indicate its direction. For example, a 10 kg ball moving at 2 m/s to the right has a momentum of +20 kg m/s and the same ball moving to the left has a momentum of –20 kg m/s. Momentum has units of mass multiplied by speed—or kilogram meters per second (kg m/s).
Positive and negative momentum
The symbol for momentum is a lower case p or vector p. Historically, momentum was identified with the persistence of an object to continue in its original speed and direction of motion. While we call it “momentum” today, Newton called “impetus” in 1760. Impetus is derived from the Latin word petere, which means to go toward.
Two different ways to have the same momentum Objects with different masses can have the same momentum. For example, a 1 kg object moving at 100 m/s has the same momentum as a 100 kg object moving at 1 m/s. Both have the same “persistence of motion” described by Newton. Because the momentum is the same, it also takes the same force exerted over the same amount of time to stop either ball even though the masses and velocities are very different.
Momentum is a fundamental quantity in physics. In the quantum world, momentum is more fundamental than either mass or velocity taken separately. Newton's first law might be more accurately named the law of momentum, because it is really momentum that remains unchanged when the net force is zero.
Which has more momentum, a 4,000 pound car traveling at 60 miles per hour or a 30,000 kg truck traveling at 1.5 meter per second? Show


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