Using Newton’s Laws
This section of chapter six is mainly over Isaac Newton’s second law, which states that the acceleration of an object is dependent upon two variables, the net force acting upon the object and the mass of the object. It also identifies the cause of a change in velocity and the resulting displacement which Newton called “a law of nature” because he thought this applied to all objects. Years later scientist found that Newton’s second law did not apply to velocities close to that of the speed of light nor for objects the size of atoms, but it continues to impact our everyday lives.
We apply Newton’s second law when measuring mass and weight. Aristotle, a greek astronomer and scientist, believed that the heavier an object is, the faster that object falls. Later on Galileo questioned Aristotle’s theory; he knew that in order to understand the true nature of the force causing an object to fall, he would have to take away the air drag. If one were to drop two equal weight objects side by side they should fall at an equal rate, correct? But what if they were to be tied together? Aristotle assumed that both would fall at a quicker speed. However, Galileo believed that it did not matter what their weight was, they gain speed at the same rate, meaning that they have the same downward acceleration. Galileo’s hypothesis was tested and found true.
The equation became F g
= mg. When one steps on a scale what is being measured? A regular scale is made up of springs which when you step on it, the scale creates an upward force on you; because you are not moving the net force is therefore zero and the magnitude of the spring equals your weight. Thus you measure your weight on a scale and not your mass. The weight force was defined as F g
= mg. The upward force applied through the floor, which opposes gravity and prevents a supported object from
falling is an object’s apparent weight. Basically, the force applied by the scale.
Weightlessness on the other hand signifies the lack of contact forces pushing up on you or your apparent weight is zero.
The friction between two or more solid objects that are not moving in the same direction is defined as static friction; it acts in response to other forces. Static friction force is written as, kinetic = μ k
. The force applied on a surface by another when both are in relative motion is the kinetic friction force and is written as, static ≤ μ s
. All surfaces are microscopically rough no matter what, so when two touch, the high spots on each are in contact and bond