GOLDEN TIPS ANSWERS GRADED A+ WITH REVEIWERS
Hooke's Law - (answers)∆F = k∆x
where k is the stiffness of the object
Stress - (answers)σ=F/A
where F is force and A is cross sectional area
Strain - (answers)ε=∆x/x
where x is the original length of the material and ∆x is the extension
Young Modulus - (answers)Stress/Strain
Tensile stress/strain - (answers)Causes the length of the material to increase, the forces act away
from the center
Compressive stress/strain - (answers)Causes the length of the material to decrease, the forces act
towards the center
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Force Extension graph - (answers)
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Stress strain graph - (answers)
Stress Strain Graphs for Different Materials - (answers)Stiffer materials have a steeper gradient.
Stronger materials have a large breaking stress
Brittle materials have a very small plastic regions
Stress Strain Graph for Rubber - (answers)
,Limit of Proportionality - (answers)*The point until which force and extension (or stress and
strain) are directly proportional. After this point it may behave elastically, but they will no longer
be proportional*
Elastic Limit - (answers)*The point beyond which the material is permanently deformed, it won't
return to it's original shape*
Yield Point - (answers)*Beyond this point the material suddenly undergoes a large increase in
extension (it 'gives') as the atomic substructure is rearranged*
Breaking stress - (answers)*The value of stress in a material when it breaks*
Elastic Deformation - (answers)*Region where the material will return to its original shape when
the stress is removed*
Plastic Deformation - (answers)*Permanent deformation caused by strain when stress exceeds a
certain value. The material won't return to it's original shape.*
Elastic Strain Energy - (answers)∆E(el) = F∆x
As this is the area under a force extension graph.
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What does it mean for a material to 阅读的”中文文章
be hard? - (answers)*It is resistant to indentation or
scratching*
What does it mean for a material to be stiff? - (answers)*It has a large young modulus and so can
withstand a large load with just a small extension*
What does it mean for a material to have a high tensile stress? - (answers)*It can withstand a
large force under tension before breaking*
,What does it mean for a material to be ductile? - (answers)*Can be drawn out into wires as it
undergoes a lot of plastic deformation*
What does it mean for a material to be brittle? - (answers)*Shatters under a sudden force as it
cracks with little or no plastic deformation just beyond the elastic limit due to the propagation of
the cracks*
Density - (answers)Density = Mass/volume
Upthrust - (answers)Due to Archemides' principle, upthrust is equal to the the weight of the fluid
displaced. This can be found if you know the density of the fluid and the volume of the object
Floating - (answers)If an object is floating, then the weight of the fluid displaced = the weight of
the object
Hydrometer - (answers)A hydrometer is an instrument for measuring the density of liquids.
The inner (solid) part of the hydrometer has a constant mass and so in different liquids it will
float to different extents
Laminar flow - (answers)-Layers are parallel to each other (don't mix)
-No abrupt changes in direction
-Fluid has a small velocity 你是想要一篇“眼睛容易
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Turbulent flow - (answers)-Layers mix
-Fluids move at a high velocity
-Abrupt changes in speed and direction
-Eddies
Viscosity - (answers)The resistance of a fluid to flowing
, Viscosity: Fluids - (answers)As temperature increases, viscosity decreases (as intermolecular
forces decrease)
Viscosity: Gas - (answers)As temperature increases, viscosity increases (as greater kinetic energy
means more collisions between particles thus more friction)
Stokes Law - (answers)F = 6πηrv
Only works for
-Small cylindrical objects
-Travelling at small velocities
-Where there is laminar flow
Terminal velocity - (answers)Need to know how to explain this as well
Terminal velocity equation derivation - (answers)-Weight = upthrust + stokes law
-m(s)g = weight of fluid displaced + 6πηrv(t)
-W(s) = 4/3 x π r^3 p(f) g + 6πηrv(t)
4/3 x π r^3 p(s) g = 4/3 x π r^3 p(f) g + 6πηrv(t)
Rearranged to make V(t) the subject and simplified you get:
v(t) = (2r^2 x g (p(s)-p(f)))/9η
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Wavelength - (answers)*The displacement between a point on a wave and the identical point on
the next wave*
Period - (answers)*The time taken for one complete oscillation*
Frequency - (answers)*The number of complete oscillations in one second*
f = 1/T
v = fλ