Chapter 1 part 5: Vectors & Momentum

                                       General Physics

• 1.8: Scalar & Vector ; centers of mass

In physics we describe certain quantities such as distance , time , weight, mass, Electric current, volume etc. We can class every kind of value into two groups, Scalar and Vector.
Every quantity has magnitude, but not all quantities have a direction.

E,G. A length of rope is described to be 10 Meters long. The magnitude of its length is 10 meters, this value has no direction as it is 10 meters long no matter what. and is therefore a scalar quantity 
But if i am measuring displacement, a vector quantity, No matter how much distance is actually traveled, the displacement is the distance from the end point to the start point, For example , a car moves 10 meters north then 10 meters West Then 10 Meters South. The car has moved 30 Meters distance wise , but has a displacement of 10 meters west of its starting point.
Vectors has magnitude and direction while scalars only have magnitude.

Every object has a center of mass , This is a point where all the weight of an object can be considered to act, if an object is tilted over its own center of mass , it will topple and fall. stable objects have very low centers of mass.
A sphere will have a center of mass right in the middle of the sphere while an upright rectangle will have one halfway up the length of the rectangle. this is why a rectangle will easily fall if you push it while a sphere will roll, since the center of mass is always in the same spot , the sphere is in equilibrium and does not move if left alone. A very unstable object may topple on its own within seconds if left alone

• 1.9: Momentum 

Any object that moves has momentum , momentum is equal to Mass.Velocity , if a moving object has a large momentum , a large force is required to stop it, Inertia is an objects tendency to stay still , so objects of high momentum have low inertia. The equation for momentum is P=M.V, where p is momentum , M is mass and V is velocity

Another quantity known as impulse is the change in momentum. A force is equal to the rate of change of momentum , so the change of momentum is newtons second law for force multiplied by time , so Impulse is equal to Force.Time

Momentum is always conserved, if an object  that is moving at a certain speed collides with another object , then the second object will start moving , gaining the momentum lost by the Initial object.
For example , if a car crashes into a garbage can that is stationary , if the car has a momentum of 500 newton meters , and the car comes to a stop at the garbage can , then the can will gain 500 newton meters of momentum, moving very quickly due to a much smaller mass.
mathematically this is shown in the equation (M1U1 + M2U2 = M1V1 +M2V2) where U is initial speed and V is final speed.