NEWTON’S 1st & 2nd Laws of Motion

Ch 12-2

Aristotle, Galileo, and Newton

Took about 2000 years to develop relationship

between force and motion.

Aristotle

Greek Philosopher. 384-322BC.Scientific discovery made

through observation and logical reasoning.

Error in theory delayed progress on motion theory 2000 yrs.

The Error: Force is required to keep an object moving at constant speed.

GalileoTheory: Gravity produces

constant accelerationUsed experiments to draw

conclusionMajor experiment: Rolled balls down a ramp and

predicted that objects remain in motion unless friction slows them

NewtonFirst defined

mass and force.1st Law.The state of motion of an object

does not change so long as the net force on the object is zero.

English: An object at rest will remain at rest until another force act on it.

NewtonInertia=Is the tendency of object to

resist change in its motion.Object at rest stays at restObject in motion stays in

motion—same direction and speed

2nd LawAcceleration = Net force(F) / Mass (m)

a = Fnet / m or Fnet = m * a

Force = mass X AccelerationMass = is a measure of inertia

an object has and depends on the amount of matter the object contains

2nd Law

The ratio is specific in that a doubling of an objects mass will cut its acceleration in half.

Weight and Mass

Weight(w) is the force of gravity(g) acting on an object. Weight = mass X 9.8m/s2 Or

W=mg Other forms:

m= W / g and g= W/ mMass is the measure of the

inertia of an object

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