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PHYSICS GCSE
Momentum and Moment (pg 12-14) T.S
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Formula for
momentum
:
M
o
m
e
n
t
u
m
=
Momentum=
M
o
m
e
n
t
u
m
=
M
a
s
s
∗
Mass *
M
a
ss
∗
V
e
l
o
c
i
t
y
Velocity
V
e
l
oc
i
t
y
Formula for
momentum
:
p
=
p=
p
=
m
v
mv
m
v
The
greater
the
mass
of an object and the
greater
its
velocity
, the more
momentum
the object has
Momentum
is a
vector
quantity - it has
size
and
direction
Momentum
is
conserved
when no
external forces
act.
Momentum before
=
momentum after
When a
force
acts on an
object
, it causes a
change
in
momentum
Formula for
force
with
change in momentum
:
F
=
F=
F
=
(
m
v
−
m
u
)
/
t
(mv-mu)/t
(
m
v
−
m
u
)
/
t
Formula for change in
momentum
:
force
=
change
in
momentum
/
time
A
larger
force means a
faster
change of
momentum
Cars
are designed to
slow
people down over a
longer
time when they
crash
- the
longer
is takes for a
change
in
momentum
, the
smaller
the
force
A
moment
is the
turning effect
of a
force
Formula for
moment
:
Moment
(Nm) =
Force
(N) *
Perpendicular distance between line of action and pivot
(m)
The
centre
of
gravity
hangs directly
below
the
point
of
suspension
A
freely suspended
object will swing until its
centre of gravity
is
vertically below
the point of
suspension
For
simple shapes
, you can find the
centre
of
gravity
by looking for
lines
of
symmetry
The principle of
moment
says that if an object is
balanced
then:
Total Anticlockwise Moments
=
Total Clockwise Moments
If a
heavy
object is placed on a
rod
, the
support closest
to the object will provide a
larger force
If the
anticlockwise
moments do not
equal
the
clockwise
moments, there will be a
resultant
moment. (So the object will
turn
)