# Is force related to Momentum?

1. Sep 10, 2007

### zeshkani

Is force related to Momentum or momentum to force in anyway
F=ma and P=mv

2. Sep 10, 2007

### Lateral

Yes, the link between the two is time. Essentially, force is applied over time to change an objects momentum.

Because F = m a, and a =$$\Delta$$v / t
then F = m v/t
As you said P = mv so we get
F = P/t or P = Ft

3. Sep 10, 2007

### Loren Booda

With calculus, the equations become more instantaneous and exact:

F=ma=m(dv/dt)=dp/dt-v(dm/dt).

If dm=0 (for instance, not a rocket) then:

F=dp/dt

4. Sep 10, 2007

### zeshkani

thx alot :)

5. Sep 11, 2007

### bsmith2000

Also, do you know the concept of Impulse? It has the same dimensions of momentum, but is more precisely defined as a Force acting over a certain amount of time. That's why when you drop an egg on a pillow, it will not break, but when you drop an egg on concrete, it will. Because the egg has some mass m and velocity v, and therefore some momentum p = mv, this momentum is numerically equal to the reactive force of the ground(or pillow) multiplied by the time interval it spends on that respective surface.

The pillow cushions the fall and therefore increases the time interval, in effect decreasing the force and keeping the egg from breaking. When you drop it on the concrete, the time interval is very short, and so the force on the egg is large (which is why it breaks).

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