CHAPTER 1

PHYSICS FOR JUNOR HIGH SCHOOL VIII

FORCE

KINDS OF FORCE

PHYSICS FOR JUNOR HIGH SCHOOL VIII

FORCE

DEFINITIONForce is propulsion or attraction given to one object

ForceTouch-force

Untouched-force

Untouched-force is a force working on one object without touching/contact it. Example of untouched-force such as gravitational-force and electrical-force.

PHYSICS FOR JUNOR HIGH SCHOOL VIII

FORCE

Touch-force is a force working on one object caused by touching

Example of touch-force such as muscle-force and shearing-force

A man is pushing a table forward, it means to give a

force on it

PHYSICS FOR JUNOR HIGH SCHOOL VIII

FORCE

1) Attraction of gravity

A force working on one object

2) Normal-force

It is a touch-force that appears by the contact of two objects

3) Force of rope-tension

A force working through rope, cable, or wire

KINDS OF FORCE IN PHYSICS

PHYSICS FOR JUNOR HIGH SCHOOL VIII

FORCE

4) Friction-force

It occurs when two objects are in contiguity

5) Force of pressure

It occurs when two objects touch each other. pressure is the rate of force for every surface-unit. It is formulated as follows :

FORCES IN PHYSICS

PHYSICS FOR JUNOR HIGH SCHOOL VIII

FORCE

The unit of force in International Unit System is Newton, or N. 1 Newton is defined as the rate of force that gives acceleration 1 m/s2 to object that has mass 1 kg. So, 1 N = 1 kg.m/s2 .

The unit of force in CAS system is dyne.

The rate of force that works on one object can be counted by using spring balance.

PHYSICS FOR JUNOR HIGH SCHOOL VIII

RESULTANT OF FORCE

Resultant of force is the combination between two or more forms of force that is produced by one object, and is united as one single force. Mathematically, it can be stated in the following figure

Mathematically, resultant of force can be stated in the following equation :

PHYSICS FOR JUNOR HIGH SCHOOL VIII

RESULTANT OF FORCE

Balanced-forceMathematically, it can be stated in the following equation:

Unbalanced-forceUnbalanced-force is a force that its dimension is not the same.

PHYSICS FOR JUNOR HIGH SCHOOL VIII

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