why is it difficult to consider the viscous drag on an object falling through a fluid?
it varies with speed, speed constantly changes due to acceleration.
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terminal velocity is reached when...
weight balances upthrust + drag
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what is viscous drag?
th friction force between a solid and a fluid
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why is it difficult to work out the viscous drag for large, fast or irregularly shaped objects?
turbulent flow creates an unpredictable situation
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weight =
upthrust + stokes force
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terminal velocity is proportional to...
the square of the radius ... so a larger sphere falls much faster
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what does hooke's law state?
that the force exerted by a spring is proportional to its extension
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what is the - sign in the hooke's law equation?
it shows that the force is the force exerted by the spring rather that the force exerted on the spring
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what is the elastic limit
the load at which the spring will remain permanently deformed once the load is removed
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larger the value of spring constant....
the stiffer the spring
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beyon the elastic limit...
materials no longer obey hookes law and may be permanently deformed if stretched further
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elastic strain energy
the energy stored in a stretched spring/ the work done by the spring.
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what is a tensile force?
one that puts something under tension
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tensile stress =
tensile force per unit area (Pa or Nm-2)
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tensile strain =
extension per unit length (no units- ration of two lengths)
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young modulus
tensile stress/ tensile strain ( same units as tensile stress- Pa or Nm-2)
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stiffer material ...
greater young modulus
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when elastic limit reached, stress and strain are...
no longer proportional
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what is necking?
when a sample begins to narrow at one point as the stress increases
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what is stiffness?
the ability of a material to resist a tensile force
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what is tensile strength?
the tensile stress at which a material fails
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compressive stress =
compressive force per unit area
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compressive strength?
the compressive stress at which a material fails
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the strength of a material refers to ...
its ability to withstand stress wether tensile,compresive or sheer.
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ductile
shows plastic deformation
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brittle
cracks or breaks with little deformation
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tough
withstand impact forces without breaking and require a large force to produce a small plastic deformation
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hard materials
resist plastic deformation by scratching, denting or cutting
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how does the mohs hardness scale work?
if a mineral can scratch another, it should be higher on the scale
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malleable
materials which show large plastic deformation before cracking or breaking
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what is the principle behind the hydrometer?
it is used to determine the density of a fluid. constant weight sinks lower in less dense fluids to displace its own weight. scale markers on the stem indicate the density of the liquid.
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how does an object dropped into a fluid float?
at the surface= no upthrust. sinks deeper= displaces greater volume of fluid, upthrust increases. upthrust = weight. object floats.
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what is a fluid?
any substance that can flow
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what is archimede's principle?
upthrust = weight of fluid displaced
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what is upthrust?
the upward force on an object submerged in fluid which is felt due to fluid pressure
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Other cards in this set
Card 2
Front
terminal velocity is reached when...
Back
weight balances upthrust + drag
Card 3
Front
what is viscous drag?
Back
Card 4
Front
why is it difficult to work out the viscous drag for large, fast or irregularly shaped objects?
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