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IB Physics HL A 2 7 Frictional Force Questions

Practise analysing HL friction systems with changing surfaces, coupled blocks, circular motion, slopes and drag.

Syllabus
First assessment 2025
Course
Physics HL
Level
HL

Exam points

  • Apply the parallel-contact friction model, distinguishing static friction up to μsFN from dynamic friction μdFN.
  • Calculate a friction force or coefficient from an inclined-plane or horizontal-surface situation, including the limiting angle or onset of sliding.
  • Determine how friction changes the acceleration, stopping distance or motion of a sliding object.
  • Analyse friction between coupled bodies or between an object and a moving surface, including whether slipping occurs.
  • Use static friction to determine limiting conditions in circular motion, such as the minimum angular speed needed to prevent sliding.

Learn this topic

Study A.2.7—Frictional force conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

IB Physics HL A 2 7 Frictional Force Questions question 1

[Maximum number: 5]

A girl on a sledge is moving down a snow slope at a uniform speed.

Figure for Question IB Physics HL A 2 7 Frictional Force Questions question 1 — IB Physics HL

Question (a)

(a)

The sledge, without the girl on it, now travels up a snow slope that makes an angle of 6.5∘6.5^{\circ} to the horizontal. At the start of the slope, the speed of the sledge is 4.2 m s−14.2 \mathrm{~m} \mathrm{~s}^{-1}. The coefficient of dynamic friction of the sledge on the snow is 0.11 .

[ 3 ]

Question (i)

(i)

Show that the acceleration of the sledge is about −2 m s−2-2 \mathrm{~m} \mathrm{~s}^{-2}.

[ 3 ]

Question (b)

(b)

The coefficient of static friction between the sledge and the snow is 0.14 . Outline, with a calculation, the subsequent motion of the sledge.

[ 2 ]
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