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Cheatography

Gravitation Cheat Sheet (DRAFT) by

for students of grade 9

This is a draft cheat sheet. It is a work in progress and is not finished yet.

UNIVERSAL LAW OF GRAVIT­ATION

every object in the universe attracts every other object with a force which is propor­tional to the product of their masses and inversely propor­tional to the square of the distance b/w them.
6.673.10-11Nm2kg-2; Henry Cavendish using a sensitive balance.

IMPORTANCE

force that binds us to earth; motion of moon around earth; motion of planets around sun; tides due to moon and sun.

ACCELE­RATION DUE TO GRAVITY

accele­ration experi­enced by a freely falling object towards the centre of the earth. 9.8 m/s2.
ER>PR = Eg<Pg
free fall: it is the object falling towards the earth under the influence of attraction force earth/­gra­vity.

MASS /\ WEIGHT

quanti­ty/­amount of matter present in an object
force by which earth attracts an object
scalar quantity
vector quantity
SI unit: kg
SI unit: N
remains constant everywhere
changes as gravity changes
can never be 0
0 at the centre of earth
WM = 1/6 WE
 

CELESTIAL BODIES: MASS & RADIUS

earth
5.98.1024kg
6.37.106m
moon
7.36.1022kg
1.74.106m

THRUST

force acting on an object perpen­dicular to the surface.

PRESSURE

thrust on unit area. SI unit: Pa or N/m2

BUOYANT FORCE OR UPTHRUST

tendency of fluids to exert upward force on an immersed object.
factors affecting buoyant force
volume of the object immersed in fluid
density of fluid
accele­ration due to gravity
temper­ature of fluidinversely propor­tional

FLOAT:
upthrust > weight of object
dfluid > dobject

SINK:
upthrust < weight of object
dfluid < dobject
density of substance is the mass per unit volume.

ARCHIM­EDES' PRINCIPLE

when a body is immersed fully or partially in a fluid, it experi­ences an upward force that is equal to the weight of the fluid displaced by it. used in designing submarines & ships, lactom­eters & hydrom­eters.
lactom­eters: determine the purity if a sample of milk.
hydrom­eters: determine the density of liquids.