UNIT - 7
FORCES AND THEIR EFFECTS
Gravity,mass and weight
https://www.pbslearningmedia.org/resource/idptv11.sci.ph
ys.maf.d4kgrav/gravity/ - Video
What is gravity?
Force between two objects that is due to their mass.
What is mass?
The amount of matter in an object. It is measured in grams or
kilograms
What is weight?
It is measure of how strongly gravity pulls on something
Drawing Forces
How can we draw forces????
There are certain rules
The direction of
the arrow shows
the direction of
the force
The length of the
arrow as to scale , to
show the size of the
force
Measuring mass and weight
◦Weight is measured in newtons
Weight = m X g
◦m = mass of the object
◦g = gravitational field strength(approx. g=10 newtons per
kilogram)
Gravitational forces between objects
◦ There is forces of gravity between any two masses
◦ Bigger the mass and the closer they are together, the bigger the
attractive force between them.
◦ The earth has a very large mass indeed, so all objects near it
experience a large gravitational pull that we call weight.
AIR RESISTANCE
The force that acts to slow down an
object moving through air. It varies with
the size and shape of the object
Friction – Force between two
surface that are pressed
together. It acts to stop the
surfaces sliding over one
another