By :- Abdus Samad KhanClass – XthSlideShare!Sam5010

Sir Isaac Newton (1643-1727) an English scientist and mathematician famous for his discovery of the law

of gravity also discovered the three laws of motion. He published

them in his book Philosophiae Naturalis Principia Mathematica (mathematic principles of natural philosophy) in 1687. Today these laws are known as Newton’s Laws of Motion and describe the motion of

all objects on the scale we experience in our everyday lives.

About Newton

Newton’s Contributions Calculus Light is composed of

rainbow colors Reflecting Telescope Laws of Motion Theory of

Gravitation

Newton’s First Law(law of inertia)

An object at rest tends to stay at rest and an object in motion

tends to stay in motion unless acted upon by an unbalanced

force.

What does this mean?

Basically, an object will “keep doing what it was doing” unless acted on by an unbalanced force.

If the object was sitting still, it will remain stationary. If it was moving at a constant velocity, it will keep moving.

It takes force to change the motion of an object.

Balanced Force

Equal forces in opposite directions produce no motion

Unbalanced Forces

Unequal opposing forces produce an unbalanced

force causing motion

If objects in motion tend to stay in motion, why don’t moving objects keep moving forever?

Things don’t keep moving forever because there’s almost always an unbalanced force acting upon them.

A book sliding across a table slows down and stops because of the force of friction.

If you throw a ball upwards it will eventually slow down and fall because of the force of gravity.

Newton’s First Law is also called the Law of Inertia

Inertia: the tendency of an object to resist changes in its state of motion

The First Law states that all objects have inertia. The more mass an object has, the more inertia it has (and the harder it is to change its motion).

Newton’s First Law (law of inertia)

INERTIA is a property of an object that describes how ______________________ the motion of the object

More _____ means More _____

much it will resist change to

mass inertia

The 1st Law

Unless acted upon by an unbalanced force, this golf ball would sit on the tee forever.

Inertia

Terminal Velocity

What We have Learnt

The first law states that if the net force (the vector sum of all forces acting on an object) is zero, then the velocity of the object is constant. Velocity is a vector quantity which expresses both the object's speed and the direction of its motion; therefore, the statement that the object's velocity is constant is a statement that both its speed and the direction of its motion are constant.

The first law can be stated mathematically as Consequently,

An object that is at rest will stay at rest unless an external force acts upon it.

An object that is in motion will not change its velocity unless an external force acts upon it.

Video – Law of Motion

MakeSureSoundIs On!

VocabularyInertia:

the tendency of an object to resist changes in its state of motion

Acceleration:

•a change in velocity

•a measurement of how quickly an object is changing speed, direction or both

Velocity:The rate of change of a

position along a straight line with respect to time

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