This Grade 12 IEB Physical Science guide covers Newton’s three laws of motion with applications, including force diagrams, frictional forces, and gravitational force calculations. It explains concepts like static and kinetic friction, free-body diagrams, and action-reaction pairs, providing stude...
I XII IIII A
nin
o static friction : frictional force on a
stationary object · acceleration inversely proportional to mass
T
note :
As the parallel component of applied force increases the
the smaller the
: a
,
magnitude of the force of static friction will increase, mass the greater
constant net force acceleration
until the maximum force of friction (ffsmax) is reached
musica
max-Msfn
Types of forces measured in newsa
· o
m (19-)
contact forces : exerted between objects in contact
connected objects :
↳ applied force tension friction
,
, normal forces.
Kinetic friction (Fk) >
objects have the same acceleration treat each object in the system as separate
< non contact forces : exerted between objects over a distance ,
note :
↳ gravitational force electrostatic force
,
,
magnetic force
> · magnitude of the force exerted on different objects by a single rope ,
bar or
Applied Force (N)
the normal force the perpendicular force exerted by a surface
:
string is the same on all objects
& Kinetic friction : frictional force that opposses the
contact with It. An applied force only acts on one object (not transferred to a connected objects
object
·
on an in
motion of a moving object and is constant while object
-
on horizontal surface :
FN =
Fg , ·
easiest to take direction of acceleration as positive
is in motion
>
pull force at an
angle :
Fr =
Fg-Fuertical example :
·
ffl =
MK FNmeasured in newtons 10kg 15kg
<
push force at an
angle
:
FN =
Fg + Fvertical Ff- IN
>
FA =
108N
&
10y
Newton's laws of motion
& Ff =
inclined plane :
10199 :
Ef
15 kg :
FA 180N
Newton's first law An object continues state of rest or
=
N T T =
:
in a
↳ When an object rests on an inclined plane the force of gravity , · 3 - ⑳ 3
uniform Velocity unless It is acted upon by a net or resultant force
FF ION
vertically down-thus force
=
acts of gravity is broken into two
7 this law applies to any object with inertia which is the property
* when a pulley is used between an object on a surface and a hanging object
components ,
Ffriction
normal
to resist any change in its state of rest motion take the direction of the hanging object as positive for the object on the surface and
T
of an object or
force
Cany object with mass has inertia -
the greater the mass the downwards as positive for the hanging object
greater the inertial -
inertia is Not a force . normal (FN) * When two hanging objects are connected by a pulley take direction of the larger
8 &
#9
[perpendicular 1 .e A seatbelt in a car exerts a net force Force (f) mass as positive
J Of ⑨
on a passenger to oppose their inevtla , seatbelt For
* objects in direct contact usings newtons third law objects exert
, ,
a force of
weight Fg// (parallel
(89) so that they don't flyout of the Windsheld J
equal magnitude and opposite in direction on eachother
o
> weight (fg)
freebody diagram
-
this is a <
lift problems :
① parallel component :
acts parallel to the slope and pulls object
Newton's second law :
When force
>
Acceleration upwards :
Tension <
Gravity ; T-Fg =
Ma
a net is applied to an object
down the incline . Fall =
Easing It accelerates in the direction of the net force . The acceleration is Acceleration downwards Tension < :
Gravity : Fg-T =
ma
② perpendicular component :
acts perpendicular to slope and pushes
directly proportional to the net force applied and inversely Gravity
< Constant Velocity/stationary :
Tension =
; Fg =
T
the object into the incline . Fg EgcosO
D
=
proportional to the mass of the object
frictional force force that opposes the motion of an object and Objects in a lift :
if an object is on a scale in a lift ,
the scale reads Fr
7
acts parallel to the surface with which the object is in contact
acceleration directly proportional
>
Acceleration upwards :
For gravity : scale reads greater than actual
weight
:
·
> the greater the coefficient of friction the greater the force constant mass
to net force > Acceleration downwards :
En > gravity ; scale reads less than actual
weight
force of friction
in Velocity/stationary FN ; scale reads actual
weight
:
< Constant =
gravity
> two types of frictional force
em
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