What two pieces of information are crucial to understanding newton's second law?

The second Newton's law of motion states that the rate of change in momentum of a moving body is proportional to the resultant force. 
Therefore, to understand this law one must understand the concept of momentum and that a body in motion experiences force.
As far as momentum is concerned it is important to note that as a body moves the momentum changes with change in time and also that a body at rest has 0 momentum because its speed/velocity is zero.
It is this change in momentum with time that is proportional to the resultant force experienced by the body.

Answer: fn = wcos50 = 38.89(9.81)(cos50) = 245.23 n

the simple machine has three main features. they are:

loadfulcrumeffort

fulcrum is the center point or pivot point of the machine. effort is input force/ applied force. load is external force/ output.

the keisha 's machine labels are

x : load

y: fulcrum

z: lever