Transcript that are in contact with each other

The meaning of Force
The effects of Forces
Types of Forces
•Frictional Force
•Elastic Spring Force
•Gravitational Force
acting upon an object as a
result of its interaction
with another object
To apply pressure against for the purpose of moving
Pushing up
Hitting a ball
Kicking a ball
Slapping
Pushing a cart
Punching
Riding a bicycle
To apply force to so as to cause or tend to cause
motion toward the source of the force.
Pulling grass
Fishing
Pulling a dog
Pulling a plug
Playing Kite
Dragging
A contact force is a force
between two objects
(or an object and a
surface)
that are in contact with
each other.
Non Contact force is a force at a
distance
It occurs between objects
not touching each other
Created whenever two
surfaces move or try to move
across each other.
The surfaces of objects are never perfectly
smooth. Even a very smooth surface seen under
a microscope, is found to have hills and
valleys. As they move across each other,
they get snagged and it makes it harder to
move.
Friction acts in the opposite direction to the movement
Friction makes it harder for things to move.
Friction acts to reduce the speed of a moving object.
Rubbing sticks to make fire
Rubbing hands causes heat
Rubbing dry sticks causes forest fire
Friction can also cause heat!
Friction is dependent
on the texture of surfaces.
Ball moves greater distance on
a smooth surface than on
a rough surface because of
lower friction
Friction is dependent on the amount of contact force
pushing the two surfaces together
Less Frictional Force
Greater Frictional Force
Friction between our shoes
and the floor stop us from slipping
Friction between the brakes
and wheel help bikes
and cars slow down
Friction between tires
and the road stop cars
from skidding
We are able to write
because of friction
present between the
paper and tip of a pen
Lighting a match stick is
possible due to the friction
between the matchstick
and its cover.
To hold a glass of
water, friction is
necessary
Friction is required to play the violin,
or to move a mouse on the mouse pad
We can not fix nail in
the wood or wall
if there is no friction.
It is friction which
holds the nail.
Friction also produces heat in machines,
when their parts are rubbed against
each other. This can lead to
over heating of the machine,
which may lead to
the damage of parts.
Tires wear out
Wears out the soles of shoes
Produces unnecessary heat - Car engines
becomes hotter because of friction.
To overcome excess
friction in air,
a lot of fuel is wasted
in cars and airplanes
If you do not oil a bicycle
the string and axes can
squeak and be noisy.
Machines wear out and need
lubrication after a period of
time due to the friction
present between
the different parts of
a machine.
Sand and gravel is strewn
on slippery ground
during rainy season
or snowy road
Patterns on the surface of tires
and on the soles of shoes
Putting nets
on sole shoes
to walk
on snowy or icy road
A carpet is used
to cover the tiled surface.
Spikes are provided in the soles
of shoes used by players and athletes
Road are made with rough
surfaces to provide grip of
vehicle tires.
An elastic spring force occurs
when a material is stretched
or compressed.
Stretching and Compressing
Elastic Spring Force
Stretched Spring
Stretched Bow
Stretched Rubber Slingshot
Stretched Rubber Band
Compressed Spring
Cloth Pin
Stapler
Elastic Band
Compressed Ball
Pins
Spring Bed
Trampoline
THE HISTORY OF GRAVITY
Sir Isaac Newton
wrote the
Law of Gravitation
in 1687
Gravity or gravitational forces
are forces of attraction.
Attracts each other
Gravity is a pulling force
Gravity is measured as an acceleration
The gravity of planet Earth is measured as 9.81 m/s2
Mass is how much matter
an object has
Mass is measured in grams (g)
or kilograms (kg)
The weight of a body is
the force
of gravity acting on it
Weight is measured in Newton's (N)
or kiloNewtons (kN)
Your mass stays the same if you could travel from planet to planet,
but your weight would vary depending on
how the gravity of that planet pulls on you.
In outer space, away from any planet or star,
an object becomes weightless