CHAPTER 2

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

NEWTON LAW

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

NEWTON LAW

Newton is British scientist who especially learns on dynamics, the branch of physics that learns on motion . He proposes 3 laws of motion.

Newton’s ideas then stated in a book titled Philosophiae Naturalis Principia Mathemathica or well-known as Principia.

The three laws about motion and force stated by Newton as Newton Law.

Both the first and the second Newton Law refer to Galileo’s theory.

The third Newton Law talks on action-force and reaction-force.

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

THE FIRST NEWTON LAW

The first Newton Law : “An object would be motionless or moving on until another force comes and changes its condition”

Mathematically, it can be stated as follows :

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

THE SECOND NEWTON LAW

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

THE SECOND NEWTON LAW

The second Newton Law : “ The acceleration that is caused by force resultant that works on one object is directly proportional to force resultant and inversely proportional to the mass”

In stating it, we have determined the proportional-constant= 1, and its unit is F, it is determined by the unit of mass and acceleration

International Unit : m=kg, a= m/s2 , F : kg m/s2 (named Newton or N)

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

THE THIRD NEWTON LAW

The third Newton Law : “if you give a force to one object (action force), you will get the same force as you give, but the direction (reaction force) is contrary with the force you give”

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

THE THIRD NEWTON LAW

There so many applications of the third Newton Law which are related to our daily life as follows:1. Kicking ball, the ball will go forward

while our foot pushed backward,2. If someone shot using a gun, the bullet

would be pushed out leaving the gun, but the gun will be pushed backward,

3. The balloon that is blown and letting go. The air would escape from the balloon, and the balloon would go forward,

4. Jet machine boosts the high-pressure gas behind, while the the plane would go ahead.

PHYSICS FOR JUNIOR HIGH SCHOOL VIII

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