Download - Structures and Mechanisms
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StructuresandMechanisms
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Structure or Mechanism?
Can you identify a Structure within this bicycle?
Can you name a mechanisms on this bicycle?
Frame = Structure
Chain and Sprocket = One example of a mechanism
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Introduction
Vehicle Frame
High Rise Building
Bridge Supporting Roadway
Residential Dwelling
Structures can be seen all around us in our everyday lives.
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Introduction
Machinery is a central part
of life today.
How many can you
identify?
Drill Tractor
Car Luas Exercise Bicycle
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Introduction
Rack and Pinion Pulley WheelsCam and Follower
All these machines have working parts called –Mechanisms
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Introduction Look at the following items.
1. Bicycle 2. Wheelbarrow
3. Wrench
Can you identify and name the mechanisms and/or structure in each of these items?
4. Entrance
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Mechanisms, Motion and Force
Mechanism
A system of moving parts that performs some function.
Motion The process of continual
change in the position of an object “movement”
Collins Dictionary
Collins Dictionary
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Motion and Force
What input is needed for a drill to work?
Input: The lever of the drill is pulled down
Output: The chuck of the drill moves down
Exertion or the use of exertion against a person or thing that resists.
Collins Dictionary
Force “Strength or Power”
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Motion There are four main types of motion.
Linear motion – Train
Oscillating Motion – Pendulum of a clock
Reciprocating Motion – Hacksaw
Rotary Motion - Shaft
Pendulum
Train
Shaft
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Motion Linear motion
– movement in a straight line
A train on its tracks moves in a linear motion
Can you give other examples of linear motion?
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Motion Reciprocating Motion
- backwards and forwards movement
The engine pistons and valves above move up and down (reciprocate) continuously.
Can you suggest other examples?
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Motion
Oscillating Motion
Forward and backward movement in an arc
The pendulum of a clock or a child on a swing
are examples of oscillating motion.
Rotary Motion
- Motion in a circular direction, which can also be called circular motion .
The wheels of a bike move in a rotary fashion.
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ForceThere are five main types of force:
1. Compression
2. Tension
3. Shear
4. Bending
5. Torsion Columns in
Compression
A rope in Tension
Pipe Bending
Torsion forces
Shear forces
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ForceCompressive and Tensile Forces
Spring in Tension, this is where a load pulls an object apart.
This is where a load presses or squashes objects together
Can crushed by compression
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Force
This is where loads push at right angles to the surface of the object. E.g. scissors
Torsion and Shearing forcesShearing Force
This is where the load
causes an object to twist
Torsion
Torsion force
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Force
This is where the load causes an object to Bend
A piece of metal
Bending a piece of metal
Bending and Static Forces
Dynamic Load – a car which is not fixed to any one specific point, e.g. a car travelling along a road
Static Load – a load which is fixed at one point, e.g. a building