stability of an object
DESCRIPTION
Stability of an object. Science Form 2 FIS CIE Year 8A & YF 3 rd Term, 2011/2012. Centre of Gravity. This is the point at which the whole weight of the body can be taken as acting through. Regular and uniform objects. The geometrical centre of some common shapes - PowerPoint PPT PresentationTRANSCRIPT
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Science Form 2
FIS CIE Year 8A & YF
3rd Term, 2011/2012
Stability of an object
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This is the point at which the whole weight of the body can be taken as acting through
Centre of Gravity
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The geometrical centre of some common shapes
This is also where the centre of gravity and the object’s weight, W, can be considered to act
Regular and uniform objects
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When more than one material makes up an object the centre of gravity will be affected.
For non-uniform shapes
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When more than one material makes up an object the centre of gravity will be affected.
For non-uniform shapes
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For some objects the CG is not located on the actual object
External CG
Ring
Stool
2 uniform perpendicular planks
This happens when the planks are of unequal
masses. Which do you think is more massive, kids?
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When an object is suspended, so that it can swing freely, it will come to rest with its CG vertically below the point of suspension
When an object is suspended
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Find the CG of an irregular shaped lamina
CG of an irregular shape
a
bc
a bc
b
a
c
plumb line
hole
Pin held by clamp
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Now, try to balance the object at that point…
Balancing Act!
a b
c
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An object is stable if it can return to its original position when tilted and released
An object is unstable if it cannot return to its original position when tilted and released
Stability
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The Traffic ConeA great example of a VERY stable object.
What features of the cone make it so stable?
- Low Centre of Gravity
- Wide base
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The position of the Centre of GravityThe Base Area
Factors that affect stability
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The position of the Centre of GravityThe Base Area
Factors that affect stability
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The position of the Centre of GravityThe Base Area
Factors that affect stability
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Lowering the Centre of GravityIncreasing the Base Area
Improving STABILITY
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Each of the diagrams on the right represent a Double Decker bus with passengers inside.
Draw out and label the one which shows all passengers on
- the lower level- the upper level- both levels
The Double Decker Bus
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If more people sit upstairs on the bus, the CG will rise/fall. This will make the bus more stable/unstable and it can be tilted by a greater/lesser angle
The bus will fall over when the CG acts inside/outside of the bus’ base
A stable object has a low/high CG and a narrow/wide base
Delete a word to complete the sentences
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Pair Do Activity 9.3 in your textbookComplete the worksheets [will be given to
each pair]
Activity Time