Please enable JavaScript.
Coggle requires JavaScript to display documents.
interactions through application of forces (what are the effects of forces…
interactions through application of forces
introduction
force is push or pull
force is all around us
almost everything we do needs a force
forces in everyday lives
whenever we push or pull object, we are said to exert force
actions such as lifting, bending, stretching, twisting or squeezing all involve pushes and pulls
what are the effects of forces
we cannot see force but we can see effects of forces on object it acts on
start
a moving object
stop
a moving object
change speed of moving object
change direction
of moving object
change size and shape
of object
can also bring about
turning effects
in objects. device that turns when force is exerted is called lever. point at which lever turns is called fulcrum. eg, seesaw, top
how can we measure forces?
measured with force meters
spring balances
extension spring balance
spring inside stretches when force pulls it
compression spring balance
spring inside is compressed when force pushes on it
SI unit is newton (N)
how do we describe motion of objects?
speed of an object depends on 2 quantities: distance(length) moved, and time taken
SI unit of speed is metre per second (m/s or m s-1)
other common units are km/h and centimetres per second (cm/s)). km/h is common unit for vehicles travelling on roads
SI unit of time is seconds. other units for time are hour and minute
we use clocks and watches. to measure time accurately, we use electronic stopwatch
speed= distance travelled/time taken
the speed equation
speed= distance/time
time=distance/speed
distance=speed x time
some forces around us
contact forces and non contact forces
contact force: acts when subject and object touch
friction
__
slows down because of force of friction
acts whenever one surface rubs against another. the surfaces can be solid, liquids or gases
opposes movement of object
also causes surfaces to heat up
can be useful
pg 101
can be a nuinsance
makes movement more difficult and wears away materials
ways to reduce friction
using smooth surfaces, ball bearings, lubricants and streamlining
non contact forces
magnetism
magnet can attract objects made from iron and steel
magnet exerts force called magnetic force/magnetism
has north pole and south pole. when like poles repel while unlike poles attract
gravity
force pulls object towards earth.
exist between any 2 objects with mass such as earth and person/any object
gravity of moon
also exerts gravity, but force is less because it is smaller than earth
can affect the earth, eg causes tides
2 high tides, 2 low tides
weight
objects have weight
measure of force if gravity exerted on object
heavier the object, greater force acting on it
is a force, so use spring balance to measure. unit of weight is newton
difference between mass and weight
SI unit of mass is kg
weight changes from earth to moon
mass stays same everywhere
pressure
can push pin into wood but cannot do so for eraser because difference in area.
force exerted acts on small area
when same force is exerted on eraser, force is spread over large area
depends on force and area
pg 106-107
calculating pressure
pressure=force/area
unit of force is newton
pascal (Pa) 1 Pa = I N/m2 is SI unit of pressure
pressure in liquid and gasses
water pressure increases as you go deeper
when go higher, air pressure decreases
pg 109
destructive forces of nature
earthquakes
tsunamis
volcanoes
typhoons
pg 110-111