Test
Density, Buoyancy and Viscosity
Este test tiene tipos de pregunta que se abren en el reproductor de siempre.
Preguntas del test (26)
1Laminar flow:
[blank_start]No abrupt[blank_end] changes in direction or speed of flow.
The layers [blank_start]don't[blank_end] mix.- ANo abrupt
- BAbrupt
- Cdon't
- Ddo
2Turbulent flow:
[blank_start]Abrupt[blank_end] changes in direction or speed of flow.
The layers [blank_start]mix[blank_end].
Contains [blank_start]eddies[blank_end].- AAbrupt
- BNo abrupt
- Cmix
- Ddon't mix
- Eeddies
- Fwhirlpools
3Moving Balls:
The direction of movement at the top of the ball (due to the spin) is a[blank_start]gainst[blank_end] the direction of air flow thus causing a [blank_start]larger[blank_end] region of [blank_start]turbulent[blank_end] flow at the [blank_start]top[blank_end].
"Dimples" on a ball [blank_start]decrease[blank_end] the area over which there is turbulent flow. The smaller the area of turbulent flow, the less r[blank_start]esistive[blank_end] force. This means there is [blank_start]less[blank_end] work done against [blank_start]air[blank_end] [blank_start]resistance[blank_end] and less [blank_start]deceleration[blank_end] so the ball can travel [blank_start]faster[blank_end].
- Alarge
- Btop
- Cturbulent
- Ddecrease
- Eless
- Fdeceleration
- Gfaster
- Hair
- Iresistance
- Jesistive
- Kgainst
4Why does turbulent flow reduce the rate flow?
- ABecause the components of the fluid follow a longer path.
- BBecause there are eddies.
- CBecause the components of the fluid are travelling faster.
5Path of a particle:
[blank_start]Turbulent[blank_end] flow is good for moving [blank_start]small[blank_end] solid particles because the eddies and [blank_start]constant changes in[blank_end] speed and direction of flow provide some [blank_start]upwards[blank_end] force which stops the particle from falling [blank_start]downwards[blank_end].
- ATurbulent
- BLaminar
- Csmall
- Dlarge
- Eupwards
- Fdownwards
- Gconstant changes in
- Hlinear
- Idownwards
- Jupwards
6Increasing temperature, decreases viscosity which makes the lubrication effect of oil better.
- AVerdadero
- BFalso
7Units of viscosity:
- APa s
- Bkg m^-1 s^-1
- Ckg m^-1 s^-2
- DPa s^-1
8Stokes' Law (F = 6πηrv):
- AF represents viscous drag
- BIf F is much smaller than the other forces (weight and upthrust) it is usually treated as negligible
- CF represents force
- DStokes' Law is for laminar flow only
- EStokes' Law is for turbulent and laminar flow
9Stokes' Law only applies to [blank_start]small[blank_end] [blank_start]spherical[blank_end] [blank_start]objects[blank_end] moving at [blank_start]low[blank_end] [blank_start]speeds[blank_end] with [blank_start]laminar[blank_end] flow.
- Asmall
- Bspherical
- Cobjects
- Dlow
- Espeeds
- Flaminar
10To find a value other than F use the fact that [blank_start]W[blank_end] = [blank_start]F + U[blank_end] (falling object) or [blank_start]U[blank_end] = [blank_start]W + F[blank_end] (rising object) to find a value for F using [blank_start]Stokes' Law[blank_end].
- AW
- BF + U
- CU
- DW + F
- EStokes' Law
11For a falling/rising object at terminal velocity:
State that W = [blank_start]U[blank_end] + [blank_start]F[blank_end] or U = [blank_start]W[blank_end] + [blank_start]F[blank_end].
Say that the forces are [blank_start]balanced[blank_end].
Therefore the [blank_start]resultant[blank_end] force is [blank_start]zero[blank_end] so there is no [blank_start]acceleration[blank_end] (so constant [blank_start]velocity[blank_end]).- AU
- BF
- CW
- DF
- Ebalanced
- Fresultant
- Gzero
- Hacceleration
- Ivelocity
12Upthrust = [blank_start]weight[blank_end] [blank_start]of[blank_end] [blank_start]displaced[blank_end] [blank_start]fluid[blank_end].
density = mass / volume so mass = [blank_start]density[blank_end] x [blank_start]volume[blank_end].
Therefore upthrust = [blank_start]density[blank_end] [blank_start]of[blank_end] [blank_start]fluid[blank_end] x [blank_start]volume[blank_end] [blank_start]of[blank_end] s[blank_start]ubmerged[blank_end] o[blank_start]bject[blank_end] x 9.81 ([blank_start]g[blank_end])- Aweight
- Bof
- Cdisplaced
- Dfluid
- Edensity
- Fvolume
- Gdensity
- Hof
- Ifluid
- Jvolume
- Kof
- Lg
- Mubmerged
- Nbject
13For an object in [blank_start]equilibrium[blank_end], upthrust = [blank_start]weight of object[blank_end]
Therefore, [blank_start]weight of displaced fluid[blank_end] = upthrust = weight of object- Aequilibrium
- Bweight of displaced fluid
- Cweight of object
14Why is the weight of an air bubble in liquid counted as negligible?
- AThe density, ϼ, of air is much less than the density of any liquid. This means the weight of an air bubble in liquid is much smaller than the upthrust and viscous drag (as W = ϼ x V x 9.81) so it becomes negligible.
- BThe density, ϼ, of air is much less than the density of any liquid. This means the weight of an air bubble in liquid is much bigger than the upthrust and viscous drag (as W = ϼ x V x 9.81) so it becomes negligible.
15For a rising object:
Initially viscous drag is practically [blank_start]zero[blank_end] so the [blank_start]resultant[blank_end] [blank_start]force[blank_end] is [blank_start]upwards[blank_end].
This means it [blank_start]accelerates[blank_end] [blank_start]upwards[blank_end].
As is accelerates, [blank_start]viscous[blank_end] [blank_start]drag[blank_end] [blank_start]increases[blank_end].
This happens until the [blank_start]upwards[blank_end] and [blank_start]downwards[blank_end] [blank_start]forces[blank_end] are [blank_start]balanced[blank_end].
When this happens the [blank_start]resultant[blank_end] [blank_start]force[blank_end] is [blank_start]zero[blank_end] so there is no [blank_start]acceleration[blank_end] and the object reaches a [blank_start]constant[blank_end] speed/velocity.
- A0
- Bresultant
- Cforce
- Dupwards
- Eaccelerates
- Fupwards
- Gviscous
- Hdrag
- Iincreases
- Jupwards
- Kdownwards
- Lforces
- Mbalanced
- Nresultant
- Oforce
- P0
- Qacceleration
- Rconstant
16For a falling object:
Initially [blank_start]viscous[blank_end] [blank_start]drag[blank_end] is practically [blank_start]zero[blank_end] so the [blank_start]resultant[blank_end] [blank_start]force[blank_end] is [blank_start]downwards[blank_end].
This means it [blank_start]accelerates[blank_end] [blank_start]downwards[blank_end].
As is accelerates, [blank_start]viscous[blank_end] [blank_start]drag[blank_end] [blank_start]increases[blank_end].
This happens until the [blank_start]upwards[blank_end] and [blank_start]downwards[blank_end] [blank_start]forces[blank_end] are [blank_start]balanced[blank_end].
When this happens the [blank_start]resultant[blank_end] [blank_start]force[blank_end] is [blank_start]zero[blank_end] so there is no [blank_start]acceleration[blank_end] and the object reaches a [blank_start]constant[blank_end] speed/velocity.
- Aviscous
- Bdrag
- C0
- Dresultant
- Eforce
- Fdownwards
- Gaccelerates
- Hdownwards
- Iviscous
- Jdrag
- Kincreases
- Lupwards
- Mdownwards
- Nforces
- Obalanced
- Presultant
- Qforce
- R0
- Sacceleration
- Tconstant
17For a rising balloon:
As the balloon rises, the density of the air [blank_start]decreases[blank_end].
Because upthrust = weight of displaced air = [blank_start]density[blank_end] x [blank_start]volume[blank_end] x [blank_start]g[blank_end], upthrust will [blank_start]decrease[blank_end] as air density decreases.
However, the lower air density would [blank_start]increase[blank_end] the volume of displaced air (V = m / ϼ) which would [blank_start]increase[blank_end] the upthrust a bit.
But, the [blank_start]decrease[blank_end] in [blank_start]density[blank_end] would have a [blank_start]greater[blank_end] effect on the overall [blank_start]upthrust[blank_end] than the slight [blank_start]increase[blank_end] in volume.
Eventually, the upthrust will [blank_start]decrease[blank_end] enough so that it is [blank_start]equal[blank_end] to the weight and the balloon will travel at constant/[blank_start]terminal[blank_end] velocity.
- Adecreases
- Bdensity
- Cvolume
- Dg
- Edecrease
- Fincrease
- Gincrease
- Hdecrease
- Idensity
- Jgreater
- Kupthrust
- Lincrease
- Mdecrease
- Nequal
- Oterminal
18Larger particles have a [blank_start]higher[blank_end] terminal velocity.
This is because Stokes' Law F = 6πηrv tells us that the [blank_start]greater[blank_end] the [blank_start]radius[blank_end], the greater the [blank_start]viscous drag[blank_end] force.
Therefore the particle will carry on accelerating [blank_start]longer[blank_end] (before it reaches terminal velocity) than a [blank_start]smaller[blank_end] particle thus reaching a higher [blank_start]terminal[blank_end] velocity.- Ahigher
- Bgreater
- Cviscous drag
- Dradius
- Elonger
- Fsmaller
- Gterminal
19As temperature increases:
- ALiquids get less viscous
- BLiquids get more viscous
- CGases get less viscous
- DGases get more viscous
20When does laminar flow usually occur?
- AWhen a fluid is flowing slowly, or when an object is moving slowly through a fluid
- BWhen a fluid is flowing quickly, or an object is moving quickly through a fluid
21When does turbulent flow usually occur?
- AWhen a fluid is flowing quickly, or an object is moving quickly through a fluid
- BWhen a fluid is flowing slowly, or an object is moving slowly through a fluid
22Upthrust is caused because the top and bottom of the submerged object are at [blank_start]different[blank_end] depths. Since p = hρg there is a difference in [blank_start]pressure[blank_end] which causes an overall [blank_start]upwards[blank_end] force known as [blank_start]upthrust[blank_end].
[blank_start]Archimedes'[blank_end] principle states that a [blank_start]partially[blank_end] or completely [blank_start]submerged[blank_end] object in a fluid will experience upthrust equal to the [blank_start]weight[blank_end] of [blank_start]displaced[blank_end] [blank_start]fluid[blank_end] because F = (h2 - [blank_start]h1[blank_end])ρ[blank_start]g[blank_end][blank_start]A[blank_end] = [blank_start]V[blank_end]ρ[blank_start]g[blank_end] = [blank_start]m[blank_end][blank_start]g[blank_end] = W.
- Adifferent
- Bpressure
- Cupwards
- Dupthrust
- Epartially
- FArchimedes'
- Gsubmerged
- Hweight
- Idisplaced
- Jfluid
- Kh1
- Lg
- MA
- NV
- Og
- Pm
- Qg
23How do submarines make use of upthrust to dive underwater and return to the surface?
- ATo sink, large tanks are filled with water to increase the weight of the submarine so that it exceeds the upthrust.
To rise to the surface, the tanks are filled with compressed air to reduce weight so that weight is less than the upthrust. - BTo sink, large tanks are filled with water to increase the upthrust of the submarine so that it exceeds the weight.
To rise to the surface, the tanks are filled with compressed air to reduce upthrust so that upthrust is less than the weight.
- ATo sink, large tanks are filled with water to increase the weight of the submarine so that it exceeds the upthrust.
24What is the equation for the extra pressure acting on an object due to a fluid?
- Ap = hρg
- Bp = h/ρg
- Cp = F/A
- Dp = VρA
25Temperature, viscosity and rate of flow:
Higher temperature means [blank_start]higher[blank_end] rate of flow, higher velocity of flow and [blank_start]faster[blank_end] terminal speed. This means the liquid [blank_start]can[blank_end] travel further in a certain time.
Lower temperature means [blank_start]lower[blank_end] rate of flow, lower velocity of flow and [blank_start]slower[blank_end] terminal speed. This means the liquid [blank_start]can't[blank_end] travel as far in a certain time.
Therefore temperature should always be a [blank_start]control[blank_end] variable in viscosity experiments.
Increasing temperature also decreases the viscosity which decreases the [blank_start]viscous drag force[blank_end] and allows an object to [blank_start]accelerate[blank_end] (resultant force no longer zero).- Ahigher
- Blower
- Cslower
- Dfaster
- Ecan
- Fcan't
- Gcontrol
- Hindependent
- Iviscous drag force
- Jaccelerate
26For an object of negligible weight, rising at terminal velocity:
[blank_start]U[blank_end] = F so [blank_start]U[blank_end] = 6πηrv
For a falling object at terminal velocity:
W = [blank_start]F[blank_end] when upthrust is negligible so [blank_start]m[blank_end][blank_start]g[blank_end] = 6πηrv
- AU
- BU
- CF
- Dm
- Eg
Información
- Descripción
- AS - Level (Materials) Sally's Physics Test sobre Density, Buoyancy and Viscosity, creado por Sally Lancaster el 05/02/2016.
- Autor
- Sally Lancaster
- Idioma
- English
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