This can be re arranged into what is known as impulse, which is force applied over a period of time in order to change an objects momentum. I = p = Ft. You will notice that impulse is equal to momentum. The units are equivalent, kg*m/s.
If an object changes mass as it delivers force (at a set velocity) that is how thrust is defined. In the case of rockets, they fire they are losing mass but continue to provide the thrust at the same speed (allowing them to accelerate and gain momentum!).
9-1
Linear Momentum: the product of mass and velocity (which is a vector, so momentum is a vector as well). It does not have a special designated unit, but its units are kg*m/s.
To stop an object must be equal (but in the opposite direction) to the amount of momentum an object currently has. In order to change its direction more momentum must be applied (in the opposite direction) than the amount the object has in its current direction.
9-2, 9-3 & 9-8
Newtons Second Law states that the force applied to an object is equivalent to the mass of the object and acceleration applied to it. However, it can be restated at the change in momentum divided by change in time. F = ma = p/t.
p = momentum
I = impulse
m = mass
v = velocity
a = acceleration
t = time
F = force
9-4
Conservation of momentum means that the momentum of a system initially has to be equal to the amount of momentum in the system in its final state. The individual pieces of the system do not need to maintain the same momentum, but their sum must be equal at all times.
9-5 & 9-6
A collision is where an object strikes another object (or surface or several other objects). INELASTIC collisions mean that momentum is conserved but kinetic energy is not conserved. imagine a moving train car striking a non moving train car, and they stick together. The result would be a slower moving two train cars. The momentum would be equivalent but the kinetic energy would be different (because kinetic is weighted more heavily on velocity - see the KE formula). An ELASTIC collision would mean that both kinetic energy and momentum have been conserved. See a newtons cradle for example.
9-7
The center of mass is crucial for calculating the movements of large, non symmetrical objects or multiple connected objects of various size (see the "fosbury flop" or "bolo weapon" for example), To find the center of mass, the product of all masses and coordinates along a coordinate line must be divided by the sum of all masses. This has to be done on the x and y axis, the two resulting answers are your coordinates. The velocity at the center of mass is equal to the sums of momentum at each part divided by the sum of the masses at each part.