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### Course: High school physics - NGSS>Unit 1

Lesson 2: Introduction to momentum

# Introduction to momentum

The momentum (p) of an object is equal to the object's mass times its velocity (p=mv). Momentum is a a vector quantity which has the same direction as velocity. Momentum is defined for a particular frame of reference. Created by Sal Khan.

## Want to join the conversation?

• If you drove the truck at 20 m/s into a stationary formula one car, assuming all the momentum was transferred from the truck into the car, would the car have a momentum of 600,000 kg*m/s just after the time of impact?

If so, could you calculate the velocity of the car?
• yes the standard unit of velocity magnitude (also known as speed ) is the meter per second (m/s). ... If you are driving the car, the velocity of the car relative to your body is zero. If you stand by the side of the road, the velocity of the car relative to you is 20 m/s northward.

hope this helped :/
• How was momentum as mass-times-velocity discovered as a significant quantity? Why not, say, mass-velocity ratio or some other quantity? How did physicists arrive at this specific product as a significant one to compute for moving objects?
• what is the difference between mass, inertia, and momentum?
• 1. Mass is the quantity of matter which an object contains.
2. Inertia is the tendency to move or stay at rest.
3. Momentum is kind of how much difficult to stop an object.

The relationship between these is if an object has more matter then it will have more inertia. So according to p=mv, it will have greater momentum.

Think about a train and a normal car. Apparently, the train has much more mass than the car. So, it will have more inertia. So when you push the breaks of these two vehicles at the same time, it will be more difficult to stop the train.
(1 vote)
• The Eighteen Wheeler Truck ... Optimus Prime!
• Why is momentum defined with a P in ?
(1 vote)

The P really stands for impetus, which is from the Latin impellere from im- + pellere. Pellere meant “to push forcefully.” As im- was a prefix meaning “inner,” impellere meant pushing with an inner source of energy. The abbreviation m isn’t available to symbolize momentum because m is used to symbolize mass.

Hope this helps!

Happy Learning!

Angelina
(1 vote)
• Want to ask in order to be certain that I understood, from my frame of reference the big stone will have a momentum of 2,000,000 Even though it's acceleration is 0? Or the fact that the stone is in pause affects it's momentum from my frame of reference?(Does the mass even matter in this case?)
(1 vote)
• If we had a scenario where the car was only moving 19 m/s rather than 20 m/s like the 30,000 kg truck, would the momentum of the truck to our frame in the car be 30,000 kg m/s from (20-19 m/s) x 30,000 kg?
(1 vote)
• KE=1/2mv^2, p=mv, therefore p=2KE/v, so as v increases p decreases. does this make sense? Thank You!
• We have p = 2KE/v, but that doesn't necessarily mean that as v increases p decreases. Note that KE is dependent on v^2, so the factor of increase in KE outweights that of v itself.
(1 vote)
• How fast would it go if it were traveling faster distance/velocity based on the rate of speed at which it was traveling?