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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