Transcript Design Technology

Grade 9 Tech. Module
Unit 2-Basic skills
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Introduction
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Topic 1: Energy Conversion
Topic 2: Measuring Energy
Topic 3: Schematics and Pictorials
Topic 4: Fabrication
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Topic 1
Energy Conversion and
Transmission
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Mass is a measure of the amount of matter in an object and is
measured in kilograms (Kg).
The mass of an object can be determined using an equal
arm balance.
Activity - Measure the mass of the provided objects.
Record the results in a table
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Force is the measurement of influences that change the direction
of an object.
Force can be measured using a spring scale calibrated in Newtons.
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Activity
- Measure the weight of an object using a spring scale.
- Measure the force required to pull the object across a
surface.
- Record the results in your table
- Describe how the mass of an object and the force
required to lift the object or drag it across a surface are
related.
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Activity
- Measure the mass of the provided objects.
- Record the results in a table
Object
Mass (Kg)
Weight (N)
Force to pull (N)
T -Square
Yellow tape
Orange tape
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Work occurs when energy gets transferred from one object to
another object.
The mathematical relationship is:
W=F×d
A few points:
• The mass has to move for work to be done on the object.
• The mass has to move in the direction of the applied force.
• Weight is equivalent to force of gravity.
• The spring scale should be parallel to the surface when
pulling the object across the table.
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W=F×d
(measured in N.m or Joules)
Activity
Part A
Determine the work done in pulling an object across a horizontal
surface.
- Measure the force to pull the object (F)
- Measure the distance you pulled the object.
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W=F×d
(measured in N.m or Joules)
Part B
Calculate the work done when the mass is lifted through a distance
- Measure the force to lift the object (F)
- Measure the distance you lifted the object.
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Example 1:
How much work is done by a person who uses a force of 30 N
to move a grocery buggy 5 m?
Given:
F = 30 N
d =5m
W =?
Solution: Use W = F x d
W = F x d = 30 N x 5 m
Answer
W = 150 J
Example 2:
55, 000J of work is done to move a rock 25m. How much force was
applied?
Given
W=55,000 J
d=25m
F=?
In this problem, we are looking for force, so the equation must be
rearranged.
Equation
F = W = 55,000J = ?
d
25m
Answer
F = 2200J
Handout: Practice exercise - work
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Topic 2
Measuring Energy and
Energy Transmission
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Voltage (V) is the difference in electric potential or the
total charge between the two terminals.
Current (I) is the rate at which the electric charges move
through the conductor.
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Power (P) is the rate at which work gets done. In the case of
electricity, we say that electrical power is the rate at which
electrical energy is transferred by an electric circuit.
Electrical Energy (E) is the scientific form of electricity,
and refers to the flow of power or the flow of charges along
a conductor to create energy.
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Electrical power (P) is defined as:
Electrical Power = Voltage x Current
or, substituting the symbols
P = VxI
(watts)
Activity
Use a multimeter to measure the current and the voltage
being used by a small bulb . Calculate the power of the bulb.
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The mathematical relationship is:
Energy = (current × voltage) × time
Energy = VIt or E = Pt (Joules)
Activity
Use a multimeter to measure the current and the voltage
being used by a small bulb over a given time. Calculate the
energy used by the bulb.
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Example 1: You have an electric heater in your room. If it
operates at 220 volts and consumes 10 amps of electricity,
what is its power rating?
Given:
V = 220V
I = 10A
P=?
Solution: Use the formula, P = IV
P = VI
P = 220V x 10A
P = 2200W (W is the same as watts)
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Example 2:
How much electrical energy (E) is consumed by a 2200 W
electric heater if it is turned on for 12 hours?
Cost = kilowatt x hours x cost/kwh
Given:
P = 2200 W = 2.200 kilowatts = 2.20 kw
T = 10 hrs
Cost/ kwh = $0.10
Cost = 2.20 kw x 10 h x $0.10/kwh
= $ 2.20
E=Pxt
E= 2200 W x 43200 sec = 95,040,000 W-s or 95,040,000 Joules
If you check your "power" bill you will find that the unit used to
measure the amount of electricity used is the kilowatt-hour and
not joules.
To determine energy cost you must change Joules to Kw-hr
1 Kw-Hr = 3,600,000 Joules
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In our heater example we use 95,040,000 Joules of energy.
95,040,000 ÷ 3,600,000 = 26.4 kw-hr
Currently, depending on where you live, a kilowatt-hour costs
about $0.09 (9 cents).
So our heated used $0.09 x 26.4 = $2.40
Not much… But in a year it adds up.
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All appliances, when new, must have a sticker attached that
indicates some of the electrical properties of the unit.
Look at the sample appliance sticker below. Circled in red is
important electrical information.
We can use this information to calculate the energy cost as
we did in the last example!
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Power is the measurement of how fast work is done.
We can also write power as:
Power = work divided by time (work in joules, time in seconds,
power in watts).
P=W ÷ t
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Example
A crane lifts a 200N crate out of a 6 meter deep hole . If it
takes 5 second to complete the task, how powerful is the cranes
engine?
Given:
F=200N
d=6m
t=5s
Solution
W=fxd
W=(200)x(6) = 1200 J
P=W ÷ t
P=(1200) ÷ (5)
P=240 Watts
Worksheet: Power and energy
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Systems that use energy to do work are not 100% efficient.
Some of the work input is turned into undesired forms of energy
such as heat and sound instead of useful work.
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Only about 15% of the energy from the fuel you put in your tank
gets used to move your car down . The rest of the energy is lost
to engine and driveline inefficiencies.
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At the power plant, some 60 percent of the energy is lost as
waste heat. Another 10 percent is lost in electricity lines and
transformers before the electricity even reaches your home.
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The efficiency of a system is mathematically determined
by the ratio of work output to work input expressed as a percent
Efficiency = (work output ÷ work input) × 100%
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Example
A winch use 120J of work to lift a 10N weight 8m high. How
efficient is it?
Given:
Work (in) = 120 J
Work (out) = ?
Efficiency=?
Solution: Work (out) = Fxd = 10x8 = 80J
Efficiency = (work output ÷ work input) × 100%
= (120 ÷80) x 100%
= 67%
The winch is 67% efficient.
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Grade 9 Tech. Module
Topic 3 Schematics
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A schematic is a diagram that represents parts of a system
using, symbols rather than realistic pictures.
You should know some of the common Electrical symbols
cell
battery
lamp
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LED
resistor (load)
switch
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ammeter
voltmeter
variable resistor
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Can you draw the schematic?
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Pictorial Drawings
Pictorial drawings are three dimensional drawings that
look similar to a picture.
There are two basic types. They are:
- Oblique
- Isometric
Isometric
The isometric drawing is most commonly used when
constructing a set of drawings.
Notice, front and side are at 30 degrees to the vertical.
Isometric
The faces of isometric are labeled by their location.
Orthographics
Often the faces are drawn separately when developing a
drawing… this is called an Orthographic.
An Orthographic projection is a series of drawings that
show various views of the object.
Sample Orthographic Drawing
Orthographic drawing of a book
Activity
Part 1 - Software- Isometric Drawing Tool
http://illuminations.nctm.org/ActivityDetail.aspx?ID=125
Handout: Illuminations Isometric Views
Part 2 - Building with blocks.
Examine objects.
•Sketch the Orthographic for each.
Examine an orthographic
•construct the object using the blocks
Production Methods
A number of methods are use to produce products.
These may include:
1. Separating
2. Combining
3. Forming
4. Conditioning
5. Finishing
Examples
1. Separating
– use of a knife, chisel, plane, or saw to cut
(separate) materials
2. Combining
– use of a nail, screw, staple, or glue to combine
materials.
3. Forming
– Use of heat and steam to form or shape materials
4. Conditioning
– Use of chemicals to condition or
protect materials
5. Finishing
– Use of sandpaper, buffing compound, or paint
to smooth and/or ‘beautify’ a project
Class Discussion
View the objects on the next few slides and
determine which production methods would be
used to produce the product.
Remember:
• Separating
• Combining
• Forming
• Conditioning
• Finishing
Grade 9 Tech. Module
Topic 4: Tools and Machines
The Tools
A variety of tools may be used to aid the
production process.
The next few slides we will examine some common
tools used for each process. See how many you
can name.
Tools
• Separating
• Combining
• Forming
• Conditioning
• Finishing
Tool use and Safety
One of the largest safety concern that cause accidents in the lab
is improper tool use.
It is important to use tools both appropriately and for its
intended use.
Before any student may enter the shop he/she must review
safety and proper use of every tool.
In the next unit we will review all safety requirements for the
shop.
And remember it’s no good to learn it if you don’t practice it.
An overview of tools in our shop
Machine Drill :Used for drilling holes through a range of materials
• There are two types, the bench drill and the pillar drill.
• Important to use the correct bits.
Twist Bit
Forstner Bit
Hole Saw
Fret Saw (Scroll Saw): Used to cut and shape light materials such
as, MDF and plywood.
• The general rule: the thicker the material, the slower the
machine operator pushes the work against the blade.
• The blade is always set up with the teeth pointing downwards
Jointer: Used for jointing a surface or edge
• Uses jointer only with the guard in place.
• Joints in direction of grain.
• Makes several multiple thin cuts rather than one heavy cut.
Planer: Used for surfacing a workpiece
• Planes in the direction of the grain.
• Never looks directly into the front or rear opening of the planer
when it is in operation.
Band Saw: Used to cut and shape light material
• Guide the work slowly; do not force the work.
• Avoid backing out from cuts
• Do not attempt to cut smaller radius than the blade will allow.
Sliding Compound Mitre Saw: Makes Standard mitre cuts (90,
45. 22.5 degrees) and Compound mitre cuts (horizontal and
vertical angle adjustment).
• Repeat cuts using a stop to reproduce exact length
• Waits until saw comes to a complete stop before removing
workpiece.
Lathe: Used to make spindles
• Rotates spindle by hand to check clearance before starting.
• Stands to one side when starting the lathe.
• Selects the appropriate cutting tools.
Hand Router
• Pattern routing with upper or lower bearing bit
• Edge routing with router fence
• Through dado or rabbet routing with guides
• Plunge base routing
Drum Sander
• Grinding
• Sharpening
• Waits until the grinder has reached full rotational speed before
placing the workpiece against the wheel.
Table Saw
• Ripping
• Crosscutting
Class Discussion:
Observe the objects on the next few slides and
determine which power tools were used to create
that product.
Safety should be a part of the shop culture. Everyone working in or
visiting a shop environment has a responsibility to be constantly
on guard, to identify actual and potential hazards, and to use
personal protective equipment in the shop.
Discussion:
Can you list some general shop safety rules?
• What Kinds of things should you look out for in the Shop?
• What Kinds of things should you look out for when using tools
*See Handout: Shop Safety Rules
Shop Emergency plan
Students should be aware of any adverse reactions or allergies that
they may have to sawdust, wood, metals or plastics or any
medical condition that could cause a problem when handling
machinery.
Make sure you disclose this information to your teacher. It would
also be a good idea to inform members in your group so they can
help minimize conditions that may cause reactions.
Safety Equipment
Safety Equipment
Safety Equipment we will use in our shop:
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Footwear
Safety glasses
Gloves
Face shields
Ear protection
First aid kit
Fire extinguisher
Dust Vacuum
Ambient Air Cleaner
Apron
Eye Wash
You must understand the correct use and/or proper fit for each
item.
Foot Wear
No open toed shoes
Eye Protection
Gloves
Kevlar
Steel Mesh
Ear Protection
First Aid Kit
Fire Extinguisher
Dust Vac
Ambient Air Cleaner
Apron
Eye Wash
Your Brain
Students must be fully aware of the
Emergency Procedures in the shop.
Know:
• Information on the Shop Emergency
Plan (handout)
• The location of First Aid kits,
eyewash stations, and emergency
exits
Handout: Shop Safety Pledge
Shop Safety sheet
Quiz: Shop Safety
It’s no good to learn it if you don’t practice it.
See if you can spot the hazards on the next few slides.