Summary OCR A level Physics A 3.2 Forces in action

_




3.2 Forces in
action

, Force ,
mass + acceleration

F- -
ma resultant
force , F , in newtons N ,



mass, m ,
in
kilograms Rg ,

acceleration ,
a ,
in metres per second
squared ,
Ms
-2




A resultant
force acting on an
object will cause the object
to accelerate in the direction of the resultant force
A force of 1 newton gives a
1kg mass an acceleration
of 1ms the direction
of the force
-2
in


Mass and weight
weight
measured
is
in
the
gravitational force acting
newtons
on the object and is



W W in newtons N
mg weight
=
, , ,



mass , m , in kilograms kg ,




kilogram Nkg
"
acceleration due to in newtons
gravity g ,
, per ,




centre of mass


The resultant
gravitational force on the object ( weight) will
act
through an
imaginary point called the centre of gravity ,


which coincides with its centre mass
of
.




To find centre of gravity
:




Make holes
along the edge of the object
•
.




• Insert a clamped pin through one of the holes
•
Allow the object to come to rest then hang ,
a pwmb line from
Draw line on the
the pin .
a
object where the pwmb line rests
•

Repeat with the other holes
The centre of is where the lines
•
gravity cross