Question

What is the physical significance of momentum. Like velocity gives us how position is changing with respect to time, what does momentum of an object show?

Answer 1

I have always thought momentum as signifying the force needed to bringing a body to rest. If something has large momentum, you need a large force to stop it. For example, a car moving with a high speed will get damaged more if it collides with a wall, than if the same car is moving with a low velocity and collides with the same wall.

Answer 2

The non-scientific meaning of 'momentum', as given in the dictionary, is 'driving power or strength'

Answer 3

I've always thought of this definition as a derived one, that is this is a case where knowing momentum is helpful, so that we can find out how much force is required to stop the object. This may be just an application of momentum.

Answer 4

Well, momentum was first talked about in Newton's Second Law, and that is where Force was defined too..So don't you think that momentum and force go hand in hand(together)?

Answer 5

true. But the dilemma in my mind is like what came first the chicken or the egg.

If the definition of force doesn't contain momentum, then it should be likewise for momentum as well. Right?

Answer 6

But isn't force defined as the rate of change in momentum? I don't know about the chicken-egg dilemma. But in this case, probably force was thought of first, because it is an everyday experience. Only Newton came later, found a quantity called momentum, and related it with force.

Answer 7

Weight is a force. How can I define weight as a change in momentum?

Answer 8

When you drop a body from a certain height in air, the action of weight changes its momentum(velocity) every second. If you calculate the change in momentum for 1 second, you will get the force.
For example, a body of 2 kg dropped from a height(initial velocity=0) will have a velocity of 10 m s-1 after 1 second. Change in momentum=2(10-0)=20=Force

Answer 9

well i was getting a little confused with static systems and the definition you gave. For example, what about static friction?

I understand force is a velocity dependent concept, but is it right to define it in terms of momentum?

Answer 10

That's what Newton defined it in his second law.
Static friction acts only when you try to move a body by applying an external force on it. This static friction is exactly equal and opposite to your external force, so as a whole there is no net force on the body, and so there is no change in momentum.
But Kinetic friction does cause change in momentum.
For now, I am very certain that this definition of force is correct. It is Newton's Second Law, after all- You can't hope to break that so easily!

Answer 11

it's correct, but just not the universal one, i guess. It's more of a relationship.

Answer 12

Well, I must say that it is very brave of you to challenge Newton's definition. I like people like that, those who stick to their ideas no matter what.
And for your delight, you might be correct. Newton's definition is centuries old. Quantum Mechanics defines momentum for a particle behaving as a wave to be:
\[p=h/\lambda\]
Which is not what Newton said. Yes, the definition is not universal. But for classical mechanics, it is correct. If you can think of any exceptions, prepare for your Nobel Prize!

Answer 13

Newton's second law, in the case of systems with variable mass (like a rocket) should be stated
\[F=\frac{dp}{dt}\]
This is in fact the correct way to state the 2nd law