DP Physics Questionbank

Description

Nature of science:

Human understandings: Understanding and modelling fluid flow has been important in many technological developments such as designs of turbines, aerodynamics of cars and aircraft, and measurement of blood flow. (1.1)

Understandings:

• Density and pressure
• Buoyancy and Archimedes’ principle
• Pascal’s principle
• Hydrostatic equilibrium
• The ideal fluid
• Streamlines
• The continuity equation
• The Bernoulli equation and the Bernoulli effect
• Stokes’ law and viscosity
• Laminar and turbulent flow and the Reynolds number

Applications and skills:

• Determining buoyancy forces using Archimedes’ principle
• Solving problems involving pressure, density and Pascal’s principle
• Solving problems using the Bernoulli equation and the continuity equation
• Explaining situations involving the Bernoulli effect
• Describing the frictional drag force exerted on small spherical objects in laminar fluid flow
• Solving problems involving Stokes’ law
• Determining the Reynolds number in simple situations

Guidance:

• Ideal fluids will be taken to mean fluids that are incompressible and non-viscous and have steady flows
• Applications of the Bernoulli equation will involve (but not be limited to) flow out of a container, determining the speed of a plane (pitot tubes), and venturi tubes
• Proof of the Bernoulli equation will not be required for examination purposes
• Laminar and turbulent flow will only be considered in simple situations
• Values of  will be taken to represent conditions for laminar flow

Data booklet reference:

International-mindedness:

• Water sources for dams and irrigation rely on the knowledge of fluid flow. These resources can cross national boundaries leading to sharing of water or disputes over ownership and use.

Theory of knowledge:

• The mythology behind the anecdote of Archimedes’ “Eureka!” moment of discovery demonstrates one of the many ways scientific knowledge has been transmitted throughout the ages. What role can mythology and anecdotes play in passing on scientific knowledge? What role might they play in passing on scientific knowledge within indigenous knowledge systems?

Utilization:

• Hydroelectric power stations
• Aerodynamic design of aircraft and vehicles
• Fluid mechanics is essential in understanding blood flow in arteries
• Biomechanics (see Sports, exercise and health science SL sub-topic 4.3)

Aims:

• Aim 2: fluid dynamics is an essential part of any university physics or engineering course
• Aim 7: the complexity of fluid dynamics makes it an ideal topic to be visualized through computer software

Directly related questions

• 16N.3.HL.TZ0.13b:

  Water flows through a constricted pipe. Vertical tubes A and B, open to the air, are located along the pipe.

  

  Describe why tube B has a lower water level than tube A.

• 16N.3.HL.TZ0.13a:

  A solid cube of side 0.15 m has an average density of 210 kg m^–3.

  (i) Calculate the weight of the cube.

  (ii) The cube is placed in gasoline of density 720 kg m^–3. Calculate the proportion of the volume of the cube that is above the surface of the gasoline.

• 17M.3.HL.TZ2.10a.i:

  Estimate the magnitude of the force on the ball, ignoring gravity.

• 17M.3.HL.TZ1.9a:

  Explain the origin of the buoyancy force on the air bubble.

• 17M.3.HL.TZ1.9b:

  With reference to the ratio of weight to buoyancy force, show that the weight of the air bubble can be neglected in this situation.

• 17M.3.HL.TZ2.10a.ii:

  On the diagram, draw an arrow to indicate the direction of this force.

• 17M.3.HL.TZ1.9c:

  Calculate the terminal speed.

• 17M.3.HL.TZ2.10b:

  State one assumption you made in your estimate in (a)(i).

• 20N.3.HL.TZ0.12a: State two properties of an ideal fluid.
• 20N.3.HL.TZ0.12c(i):

  Determine the force exerted by the spring on the sphere when the sphere is at rest.

• 20N.3.HL.TZ0.12c(iii):

  Outline the effect on $\mathrm{Q}$ of changing the oil to one with greater viscosity.

• 20N.3.HL.TZ0.12b:

  Determine the terminal velocity of the sphere.

• 17N.3.HL.TZ0.11b:

  The room temperature slightly increases from 25 °C, causing the buoyancy force to decrease. For this change in temperature, the ethanol density decreases from 785.20 kg m^–3 to 785.16 kg m^–3. The average viscosity of ethanol over the temperature range covered by the thermometer is 0.0011 Pa s. Estimate the steady velocity at which the 25 °C sphere falls.

• 17N.3.SL.TZ0.11a.i: Identify the mechanism leading stars to produce the light they emit.
• 17N.3.SL.TZ0.11a.ii:

  Outline why the light detected from Jupiter and Vega have a similar brightness, according to an observer on Earth.

• 17N.3.SL.TZ0.11b.i: Outline what is meant by a constellation.
• 17N.3.SL.TZ0.11b.iii:

  Show that the distance to Vega from Earth is about 25 ly.

• 17N.3.HL.TZ0.11a.i:

  Using the graph, determine the buoyancy force acting on a sphere when the ethanol is at a temperature of 25 °C.

• 17N.3.SL.TZ0.11b.ii: Outline how the stellar parallax angle is measured.
• 17N.3.HL.TZ0.11a.ii:

  When the ethanol is at a temperature of 25 °C, the 25 °C sphere is just at equilibrium. This sphere contains water of density 1080 kg m^–3. Calculate the percentage of the sphere volume filled by water.

• 18M.3.HL.TZ1.10c.ii:

  Outline whether it is reasonable to assume that flow is laminar in this situation.

• 18M.3.HL.TZ1.10a:

  State the difference in terms of the velocity of the water between laminar and turbulent flow.

• 18M.3.HL.TZ1.10b:

  The water level is a height H above the turbine. Assume that the flow is laminar in the outlet pipe.

  Show, using the Bernouilli equation, that the speed of the water as it enters the turbine is given by v = $\sqrt{2gH}$.

• 18M.3.HL.TZ1.10c.i:

  Calculate the Reynolds number for the water flow.

• 18M.3.HL.TZ2.10a:

  Show that the velocity of the fluid at X is about 2 ms^–1, assuming that the flow is laminar.

• 18M.3.HL.TZ2.10b.i:

  Estimate the Reynolds number for the fluid in your answer to (a).

• 18N.3.HL.TZ0.10b.ii:

  The density of water is 1000 kg m^–3. Calculate u.

• 18N.3.HL.TZ0.10a: An ice cube floats in water that is contained in a tube. The ice cube melts. Suggest what...
• 18N.3.HL.TZ0.10b.i: Outline why u = 4v.
• 19M.3.HL.TZ2.13c:

  The weight of the sphere is 6.16 mN and the radius is 5.00 × 10^-3 m. For a fluid of density 8.50 × 10² kg m^-3, the terminal speed is found to be 0.280 m s^-1. Calculate the viscosity of the fluid.

• 19M.3.HL.TZ2.13b: Explain why the sphere will reach a terminal speed.
• 19M.3.HL.TZ2.13a:

  Draw and label the forces acting on the sphere at the instant when it is released.

  

• 19M.3.HL.TZ1.10a:

  State one condition that must be satisfied for the Bernoulli equation

  $\frac{1}{2}$ ρv² + ρgz + ρ = constant

  to apply

• 19M.3.HL.TZ1.10b.ii:

  Calculate the difference in pressure between X and Y.

• 19M.3.HL.TZ1.10b.iii: The diameter at Y is made smaller than that at X. Explain why the pressure difference between X...
• 19M.3.HL.TZ1.10b.i: Outline why the speed of the gasoline at X is the same as that at Y.
• 19N.3.HL.TZ0.9a:

  Explain why the levels of the liquid are at different heights.

• 19N.3.HL.TZ0.9b:

  The density of the liquid in the tube is 8.7 × 10²kg m^–3 and the density of air is 1.2 kg m^–3. The difference in the level of the liquid is 6.0 cm. Determine the speed of air at A.