What is the difference between momentum and kinetic energy?

[tiny-tim]

why is the force F=m_1*v_1??

ah, that's not ordinary force (= rate of change of momentum),

that's impulsive force (= total change of momentum) …

see the definition at para. 233 on page 137 of Smith.

Nowadays, we say "impulse" instead of "impulsive force", and the impulse obviously is the extra momentum, m₁v₁.

 

[aloshi]

Hello!
English is too difficult to comprehend
I have read the definition at para. 233 on page 137 of Smith.
could not really understand how he came to the F = mv.

 

[tiny-tim]

impulse

Hello aloshi!

could not really understand how he came to the F = mv.

It's a definition …

an impulse (an impulsive force, in old language) is defined as the amount of momentum that it will give something.

So if an impulse F is applied to a mass m, it gives it a momentum F, and so its speed is F/m.

If the same impulse is applied to a mass 2m (twice as massive), it also gives it a momentum F, but this time its speed is F/2m.

Impulse = increase in momentum.

 

[aloshi]

excuse me for (excuse my) disturbing you, doesn't admit of [any] solution.
is still being discussed what is the meaning of momentum?

 

[tiny-tim]

momentum is mass times velocity.

momentum = mv.

 

[aloshi]

but it inconceivable, mathematically is momentum the mass times velocity.momentum = mv.

 

[tiny-tim]

but it inconceivable, mathematically is momentum the mass times velocity.momentum = mv.

I'm not sure I understand you …

you seem to be repeating what I've just said.

What do you mean by "inconceivable"?

 

[aloshi]

What do you mean by "inconceivable"?

incomprehensible, /inconceivable, /unimaginable


mathematically, I can understand. but physically, I can not understand what means whith momentum

 

[tiny-tim]

Well, momentum is a very easy concept.

Momentum is fundamental to dynamics.

It's even more fundamental than energy, since total momentum is conserved even when total mechanical energy isn't.

A standard equation in collisions is m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂

(where u is velocity before, and v is velocity after)

 

[hsnhajiani]

what do you mean when you say the energy doesn't change the motion and it only makes some heat or some voice?
and please check whether the following statements are true or not:
the Force changes the velocity, the the impulse changes the momentum, the Work changes the energy(or the work is a method of changing the type of energy from potential to kinetic and vice versa), the momentum changes the motion, and..

i had another question too, please answer:
what is the exact definition of work(i know that Work=Force*Distance)?
well, i think there are two possible, exact definitions;
1. the work is the pure force, multiplied by the distance along which the force is being applied to the object.
2. the work is the pure force, multiplied by the distance the object has traveled (or has been displaced).

 

[danielatha4]

"mv = d/dt (1/2 mv^2)"

Do you mean...

mv = d/dv (1/2 mv^2) ??

wouldn't d/dt (1/2 mv^2) = mv(dv/dt) ?