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IB Physics SL A 2 10 Viscous Drag Questions

Practise IB Physics SL A.2.10 by explaining viscous drag, terminal speed and the balance of vertical forces in a fluid.

Syllabus
First assessment 2025
Course
Physics SL
Level
SL

Exam points

  • Use force balance and Fd = 6πηrv to calculate terminal speed for a small sphere or bubble in a viscous fluid.
  • Determine fluid viscosity or another Stokes-law quantity from measured speed, sphere radius, density and terminal-motion data.
  • Predict how viscous drag or terminal speed changes with fluid viscosity, sphere radius, density or speed.
  • Explain from changing drag and resultant force why a sphere’s acceleration decreases and its velocity approaches a constant terminal value.

Learn this topic

Study A.2.10—Viscous drag conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Physics SL A 2 10 Viscous Drag Questions question 1

[Maximum number: 4]

A spherical oil droplet is released from rest at the bottom of a column of water.

The graph shows the variation with time t of the vertical velocity of the oil droplet.

Figure for Question IB Physics SL A 2 10 Viscous Drag Questions question 1 — IB Physics SL

Question (a)

(a)

Describe why the acceleration of the oil droplet changes.

[ 2 ]

Question (b)

(b)

Explain why the velocity of the oil droplet is constant for t>3 st>3 \mathrm{~s}.

[ 2 ]
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