Newton’s Laws
History of Development
Aristotle (384-322 BC)- Ancient Greece Philosopher- All objects
have a natural resting place and move to seek that place.
Motion is classified as either Natural or Violent.
Galileo Galilei (1564-1642) All objects fall at the same rate (9.8
m/s2) and the rolling ball experiment. An object that is rolling
would continue to roll to try and reach its original starting
point. (An object in motion remains in motion)
Sir Isaac Newton (1642-1727) - Developed Calculus at 19 years
of age. Law of Universal Gravitation, Three Laws of Motion.
1st Law- Inertia- (resistance to change)- Objects at rest remain
at rest, objects in motion remain in motion UNLESS an outside
Force acts on them.
If objects are at rest, then we say that they are in equilibrium.
2nd Law- (Fnet = ma) the acceleration of an object is directly
proportional to the Net Force acting on the object and inversely
proportional to the mass. The Force and acceleration vectors
point in the same direction.
Weight is the force of gravity acting on a mass. W = mg
1 Newton = 1 kg m/s2 Newton is the unit of Force.
3rd Law- (Action/Reaction)- For every action force, there is an
opposite and equal reaction force. Forces occur in pairs!
Newton’s Laws
Forces are equal and opposite but act on different masses, so
they do not always produce the same acceleration.
Free Body Diagrams- a pictorial representation of the forces
acting on an object. Usually arrows drawn and labeled to show
the direction of the forces. These are used to help solve
problems, and determine the net force acting on an object.
When drawing, start with gravitational force, (weight), and
Normal Force.
Normal Force- (FN or N) the support force that a surface
provides in reaction to the weight of an object. The Normal
force will ALWAYS be perpendicular to the surface.
Friction Force (f) a resisting force that occurs between the
surfaces of two objects. f = N. On a flat surface, the Normal
force is equal to the weight of the object.
Two types of friction- Static- non-moving
Kinetic or Sliding- moving
Coefficient of Friction () is the ratio of two forces, f/N. There
are no units for .