CHAPTER 8 FORCE AND MOTION
CHAPTER OUTLINE
8.1 FORCE
q 8.2 EFFECT OF FORCE
q
8.1 FORCE
Describe and communicate about force.
v Explain that force has magnitude, direction
and point of application.
v Measure force in S.I unit.
v
v
Explain with examples that every action
force has an equal (same magnitude)
reaction force but in the opposite direction.
TYPES OF FORCES
GRAVITATIONAL
FORCE
FRICTIONAL
FORCE
NORMAL FORCE
BUOYANT
FORCE
WEIGHT
ELASTIC FORCE
GRAVITATIONAL FORCE
The force that
points towards
the centre of
the Earth.
FRICTIONAL FORCE
The force that
resists movement
between two
surfaces that are
in contact with
each other.
BUOYANT FORCE
The thrust force
acting on an
object that is
floating on the
surface of a
fluid.
NORMAL FORCE
The force
produced when
an object is in
contact with a
surface.
WEIGHT
The
gravitational
force acting
on it.
ELASTIC FORCE
Exists when a
material is
stretched or
compressed.
CHARACTERISTICS OF FORCE
Magnitude
Direction
MEASUREMENT OF FORCE – SPRING BALANCE
S.I UNIT OF FORCE = NEWTON (N)
ACTION-REACTION PAIR
NEWTON’S THIRD LAW
Every action force,
there is a reaction
force of the same
magnitude but in the
opposite direction
8.2 EFFECTS OF FORCE (Part 1)
q
Describe and communicate the effects of force
q
Explain and communicate the relationship
between the differences in density and the
effects of buoyancy in daily life
q
Classify and solve problems involving levers
based on the position of fulcrum, load and effort
q
Explain and communicate about moment of force
EFFECTS OF FORCE
size
FORCE
CAN
CHANGE
shape
motion
Force can move a stationary object
Force can stop a moving object
Force can change the speed of an object
Force can change the direction of
motion of an object
Force can change the shape and size of
an object
BUOYANT FORCE = ACTUAL WEIGHT – APPARENT WEIGHT
10N
10N
10N
5N
An object will float if F > W
W
F
An object will sink if F < W
W
F
PLIMSOLL LINE
LEVER
A BAR THAT ROTATES ON A FIXED POINT
ADVANTAGES
OF LEVER
A lever allows us to do
work easily
A lever allows us to use
minimal force to do work
CLASSIFICATION OF LEVER
Effort:
Force applied on the bar
Fulcrum
Load:
Object to be moved
Fulcrum
Fulcrum:
Fixed support point
Fulcrum
THE MOMENT OF FORCE – The turning
effect produced
Allows us to do
work easily
Depends on the
force applied and
the perpendicular
distance of the
fulcrum to the force
Moment of force (N m) = Force (N) x Perpendicular distance from the pivot to the force (m)
How to
increase
moment
of
force?
Apply a greater force (>N)
Increase the distance between
pivot to effort (>m)
Principle of moments of lever
Load (N) x Distance of load from fulcrum (m) = Effort (N) x Distance of effort from fulcrum (m)
8.2 EFFECTS OF FORCE (Part 2)
q Elaborate
and communicate about gas
pressure based on the kinetic theory of gas
Explain and communicate the existence of
atmospheric pressure and the effects of
altitude on atmospheric pressure
q Explain the effects of depth on liquid
pressure
q
PRESSURE – LESSON OUTLINE
Define
pressure
Application
of pressure
Gas / Air
pressure
Application
of concept
of air
pressure
Atmospheric
pressure
Liquid
pressure
Pressure:
Force per unit area
Pressure (Pa) =
Force (N)
Surface area (m2)
APPLICATION OF PRESSURE IN DAILY LIFE
GAS/AIR PRESSURE
KINETIC THEORY OF GAS
Air molecules always
move about freely and
collide with the walls of
its container
FACTORS AFFECTING AIR PRESSURE
VOLUME
TEMPERATURE
RELATIONSHIP BETWEEN VOLUME AND PRESSURE
RELATIONSHIP BETWEEN TEMPERATURE AND PRESSURE
ATMOSPHERIC PRESSURE
Pressure exerted by the atmosphere on the surface
of the Earth and all objects on the Earth
APPLICATION OF THE CONCEPT OF AIR PRESSURE
PLUNGER
VACUUM
CLEANER
MAGDEBURG
HEMISPHERE
APPLICATION
SYRINGE
SYPHON
ATMOSPHERIC PRESSURE AT DIFFERENT ALTITUDES
EFFECTS OF DEPTH ON LIQUID PRESSURE
EFFECTS OF DEPTH ON LIQUID PRESSURE
IN DAILY LIFE
EFFECTS OF DEPTH ON LIQUID PRESSURE
IN DAILY LIFE