STRUCTURE AND MECHANISM.ppt

1
THE UNIVERSITY OF TRINIDAD
AND TOBAGO
CENTRE FOR EDUCATION
PROGRAMMES
BACHELOR OF EDUCATION
CORINTH CAMPUS
STRUCTURES AND
MECHANISMS
B. RAMESAR
2012/2013
"Promoting Excellence In
Learning and Teaching"

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(I) Descriptions of technology
• The term technology connotes different
things to different people.
• To some people it represents complex
electronic devices and difficult to
understand equipment.
• To others it is the cause of all the changes
that are occuring in the world.
• Others fear it while still others see it as
some thing that enhances life.

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• TECHNOLOGY is not necessarily a
complex or space age phenomenon.
• It can be primitive and crude or it can be
complex and sophisticated.
• Technology has been here as long as
humans have been on earth.

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• TECHNOLOGY is humans using objects
tools, machines, systems and materials to
change /control the natural and human-
made environment.

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The four main characteristics of
technology
• It involves human knowledge
• It uses tools equipment, materials and
systems.
• It produces artefacts/human-made things
and other outputs eg pollution and scraps.
• It is developed by humans in an attempt to
change /control the environment, to
enhance life or to satisfy a need or want.

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• Technology is constantly changing and
always seems to be improving on existing
technology.
• It is the nature of technology that
technological solutions often create new
needs or problems and so technology is
dynamic.

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Difference between science and
technology
• Technology concerns the application of
knowledge to the solution of problems.
• Science is the pursuit of knowledge about
the universe and how it works with no
short term objectives for practical
applications.
• The two, science and technology, are
interdependent yet distinct.

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DIFFERENCE BETWEEN SCIENCE AND
TECHNOLOGY
• Science is driven by curiousity.
• It is primarily concerned with “what is”.
• Technology is driven by needs and wants
and is concerned with “how to”
• Science and technology have research as
an important activity.
• They both make use of various kinds of
processes

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USING TECHNOLOGY
• The use of technology can have adverse
effects on the environment.
• Improper disposal of industrial wastes.
• Use of fossil fuels.
• Radioactive waste produced from nuclear
energy.
• Use of pesticides in agriculture.

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(iii)TECHNOLOGICAL
PROCESSES
• Technology is both product and processes
• Technological processes can be viewed
as cyclical.
• It begins with the identification of a
problem/need or want.
• [I results in the creation of a solution to
that problem.

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CYCLIC NATURE OF
TECHNOLOGY
• Since technological solutions often creates
new needs/wants/problems. It is in the
nature of technology to be cyclic.

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(iii)TECHNOLOGICAL
PROCESSES
i

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(iv) Using Technological Processes
• Prepare an artifact (which you may use later as
a teaching resource). The artifact can be a
powered toy.
• (i) Describe the technological processes that
were in action during each stage of the artefat’s
development.
• (ii) State the scientific principles/concepts the
artifact can demonstrate.
• (iii) Explain how it may be used for teaching.

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(v) RELATIONSHIP BETWWEEN FUNCTION
AND FORM OF STRUCTURES
• INTRODUCTION objects and structures
have distinctive shapes, patterns and
purposes.
• Categories of structures-
• Solid structures; stone walls, dams.
• Frame structures; bridges, bicycles,
• Shell structures; tents, domes.

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FUNCTION AND FORM OF STRUCTURES
• The form or structure of objects enable
them to perform essential functions.
• This occurs everywhere in both the natural
and human-made world.
• consider the hammer – length of handle
shape ot claw.
•

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• Screwdrivers

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• Explain the structure and function of the
following
• House ,car, bridge, chair umbrella,
wheelbarrow

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• Structures are similar
to and different from
others in form and
function.
• Rooms have walls but
are different in size
and are used for
different purposes.
• Rubber balls are
round and solid. "Promoting Excellence In

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Ballons are round and hollow

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• Observe your hand

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• Which structural features of your hand
make it well suited to its function.
Structural features include –
• Number of fingers.
• Number and location of joints.
• Position of joints on fingers.
• Ability to move thumb across hand.

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• Activity 1
• Tape thumb to hand
• Try to pick up coin, pencil, marble,
paperclip.
• Activity 2.
• Tape fingers together and free thumb.
• .Try to pick the objects

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• Activity 3
• What kind of activities would be more
difficult with only one giant bendable
finger?
• Activity 4
• Design an activity to lift a device to lift a
marble out of a glass.

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(vi) POSITION AND MOVENENT OF
OBJECTS
• Moving things helps us develop –
• A sense of space.
• An understanding of the relationship
between stationary and moving objects
including ourselves.

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POSITION AND MOVENENT OF
OBJECTS
• MECHANISMS hinges
• Identify the simple machine
within it

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OBJECTS
• MECHANISM -
Inclined plane Identify
the simple machine

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OBJECTS
• MECHANISM –
Wheel and axl
• Identify the simple
machine within it.

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POSITION OF OBJECTS IN RELATION TO
OTHER OBJECTS
• Over

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OTHER OBJECTS
• Under
Rabbit is
under the
bed

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OTHER OBJECTS
• Beside

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OTHER OBJECTS
upwards

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PATTERN OF MOVEMENT
• Turning

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PATTERN OF MOVEMENT
• Spinning (wheels)

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PATTERN OF MOVEMENT
• Swinging

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PATTERN OF MOVEMENT
• Bouncing

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PATTERN OF MOVEMENT
• Vibrating (duckling)

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MOTION/MOVEMENT
• Movement of a trolley
released on a ramp.
• Observe
clockwise/anticlockwi
se motion of wheels.
• Observe effect
with/without load.

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MOTION/MOVEMENT
• Predict the effect of changing the slope of
the plane on the motion of the object.

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MOTION/MOVEMENT
• Predict the effect of
different surfaces of
the plane on the rate
an object slides
down.
• Wooden surface
• carpet surface
• Tile surface

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Moving a load
• Predict what factors do you do you think
makes a load heavier /easier to move?
• Size of wheels (LARGER WHEELS make it
even easier).
• With hinges;
• friction

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• Rolling Resistance The ease of moving a piece of
equipment is determined by the resistance of the wheels
to rolling. Rolling resistance is described as 'that effort
required to move equipment from rest to keep it moving'.
The easiest rolling is achieved by HARD TYRED
WHEELS on a hard smooth surface. However, if the
wheels must overcome obstacles then the effort required
includes the force needed to lift the wheels over
obstructions.RESILIENT TYRED WHEELS roll over
these obstructions.BEARING WHEELS make it
easier.LARGER WHEELS make it even easier.With so
many variations to consider, the only realistic
measurement of rolling resistance is actual site testing.

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(viii) ACTION OF FORCES ON
OBJECTS/STRUCTURES
• Forces that act on structure -
• Mass
• Air resistance
• Structures are under -
• Tension
• Compression

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Tension
• Tension is a reaction force applied by a
stretched string (rope or a similar object)
on the objects which stretch it. If an object
hangs from a rope due to gravity, the
gravitational force on the object points
downward, and there is an equal tension
force in the rope point upward, making the
net force on the object equal to zero.

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Tension
• Wires in a suspension bridge is under
tension

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Compression
Compression testing compression springs
machine

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MOTION
• Linear motion eg a
sliding door
Push /pull motion

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MOTION
• Rotational motion

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MOTION
• Oscillations

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MOTION
• Reciprocating motion - is a back and forth
motion

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MOTION
• The magnitude of forces that act on
objects. devices, systems, determine –
• speed and also direction of motion.
A force produces a change in speed (an acceleration)
In the absence of force,
objects move at a steady speed,
or remain stationary

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MOTION
What can a force do to an
object?
• Forces can:
• Cause and acceleration
• Speeding up
• Slowing down
• Change direction
• Do nothing
• Cause work (w = Fd)
• Change shape

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MOTION
• Some mechanisms change one type of
motion to another type of motion
• E.g a screw – it rotates but creates a linear
movement
• A motor engine rotates, the pistons moves
in a reciprocating manner which causes
the wheels to rotate and enables the car to
move in a linear way.

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MOTION
• Rack and pinion

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LEVERS

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LEVERS
• FIRST CLASS LEVER; FULCRUM IS
BETWEEN LOAD AND EFFORT

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EXAMPLE OF FIRCT CLASS LEVER
• CAN OPENER

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FIRST CLASS LEVER CROW BAR
• IDENTIFY LOAD, EFFORT AND
FULCRUM

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FIRST CLASS LEVERS
• Identify load effort and fulcrum

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SECOND CLASS LEVERS
• Identify load effort and fulcrum

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Examples of second class levers
• Tdentify load effort and fulcrum

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THIRD CLASS LEVERS

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• Nail clipper, twezer and tong

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• Ramps, sloping roads, chisels,
hatchets, carpenter's planes---all of
these are examples of the basic
machine: The inclined plane and its
active twin brother the wedge. In the
broadest sense, the wedge includes all
devices for cutting

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Inclined plane

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GEARS
• A gear is a component within a
transmission device that transmits
rotational force to another gear or device.
A gear is different from a pulley in that a
gear is a round wheel which has linkages
("teeth" or "cogs") that mesh with other
gear teeth, allowing force to be fully
transferred without slippage

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gears
• IDENTIFY
DIRECTION

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PULLEYS
• A pulley (also called a sheave or block) is
a wheel with a groove between two
flanges around its circumference. The
groove normally locates a rope, cable or
belt. Pulleys are used to change the
direction of an applied force, transmit
rotational motion, or realize a mechanical
advantage in either a linear or rotational
system of motion

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PULLEYS
• Single fixed pulley
• Load=effort
• No mechanical
advantage

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• Single moving pulley
• Load=2xEffort

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FRICTION
• Friction is the force of two surfaces in
contact, or the force of a medium acting on
a moving object (i.e air on an aircraft

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• When contacting surfaces move
relative to each other, the friction
between the two objects converts
kinetic energy into thermal energy, or
heat

STRUCTURE AND MECHANISM.ppt

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