FORCES
Definition
A push or a pull that one object exert on another
Effects of forces
Start or stop the motion of an object
Change the size and shape of an object
Increase or decrease the speed of a moving
Change the direction of motion of a moving object
Cannot be seen but the effects can be seen
and felt
Affects speed and distance travelled
Size of force applied is proportional to distance and speed of object
Greater force applied , greater distance travelled
Affects speed and distance travelled
Forces of nature
Useful
Harmful
Help to do work
Cause destruction
Wind turns windmill
Water turns water wheels
Volcano eruption š
Tsunami or tidal waves
Forces of nature
Friction ( frictional force )
Characteristics
Exists between surfaces that are rubbing against each other
Reduces speed of moving objects
Produces heat
Opposes motion
Rougher surfaces
Greater friction
Produces more heat
Uses of friction
Allows us to control movement
Reduces slipping
Produces heat
Problem caused by friction
Wear and tear
Machines work less efficiently
Make things overheat
Object move slowly
Methods to reduce friction
Putting lubricant
Rollers , ball bearings and wheels
Streamlined body
Elastic Spring Force
Change shape when a force acts on them but will return
to original shape
When an object is stretched or compressed, it exerts
a force on the object stretching or compressing it
Gravity
Force between Earth and all objects
All objects have the same amount of gravitational force
Affected by
Difference
Magnetic force
Definition
Weight is the amount of gravitational force acting on an object.
Mass is the amount of matter in an object
Force that is exerted by magnets and magnetic materials
Attraction
A pulling force
Causes magnets to attract magnetic materials
Causes magnets to attract unlike poles of other magnets
Can use for testing if an object is a magnetic material
Cannot use to test if an object is a magnet
Repulsion
Can be used to test if an object is a magnet or a magnetic material
A pushing force
Causes magnets to repel like poles of other magnets