LESSON 8 NEWTON'S LAW OF MOTION

Aristotle

• on (384-322 BCE), he believed that a force was necessary to keep an object in motion

Galileo

• On (1564-1642), he challenged the idea of Aristotle

• He found that objects resist changes in motion (inertia) and that, in the absence of friction, they would continue moving indefinitely - an idea that laid the groundwork for newton’s first law

Isaac Newton (1642-1727)

• In 1678, he published his landmark book PHILOSOPHIA NATURALIS PRINCIPIA MATHEMATICA (principia)

• In it, he formulated the 3 laws of motion, which described the relationship between an object and the force acting on it

First law

Law of inertia

Second law

F=ma this became the cornerstone of classical mechanics

Third law

For every action, there is an equal and opposite reaction

First law of motion

• Law of inertia

• An object remains at rest or in a uniform straightline unless it is compelled to change by an externally imposed unbalanced force

• Tendency to resist changes in their state of motion

• Every body continues in it's state of rest, or in uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it

• Example is a soccer ball waiting to be kicked and a billiard ball waiting to be hit

Second law of motion

• F=mass x acceleration

• The acceleration of an object is directly proportional to the magnitude of imposed force and inversely proportional to the mass of the object

• The change of motion is proportional to the motive force impressed, and is made in the direction of the right line in which that force is impressed

• Example is it is easier to push an empty shopping cart than a full one because the full one has a bigger mass than an empty one

Mass (kg)

It is a measure of the amount of matter in an object

Acceleration (m/s²)

It is the rate at which an object’s velocity changes overtime

Force (N)

It is a push or pull acting on an object that causes it to accelerate

Weight (N)

It is the force of gravity acting on an objects mass

Third law of motion

• For every action, there is an equal and opposite reaction

• Whenever objects A and B interacts with each other, they exert forces upon each other

• Example is When you jump off a small boat, you push the boat backward while you move forward