IB Physics SL A 2 26 Angular and Linear Speed Questions

Practise using v = ωr and v = 2πr/T to calculate angular speed, tangential speed, period and orbital speed in wheels, pulleys and satellites.

Exam points

Convert angular speed, period and frequency, then calculate tangential speed with v = ωr in rotating systems.
Use v = 2πr/T to determine orbital or turntable speed, keeping radius, diameter and SI units consistent.
Compare changes in radius or rotation using linear speed, angular speed, direction and torque effects.

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Study A.2.26—Angular and linear speed conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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This question is in two parts. Part 1 is about two children on a merry-go-round. Part 2 is about electric circuits.

Part 1 Two children on a merry-go-round
Aibhe and Euan are sitting on opposite sides of a merry-go-round, which is rotating at constant speed around a fixed centre. The diagram below shows the view from above.

Figure for Question IB Physics SL A 2 26 Angular and Linear Speed Questions question 1 — IB Physics SL

Aibhe is moving at speed $1.0 \mathrm{~ms}^{-1}$ relative to the ground.

Aibhe moves so that she is sitting at a distance of 0.75 m from the centre of the merry-go-round, as shown below.

Euan pushes the merry-go-round so that he is again moving at $1.0 \mathrm{~ms}^{-1}$ relative to the ground.

Determine Aibhe's speed relative to the ground.

Aibhe's period of revolution is the same as before;
from $v=\frac{2 \pi r}{T}$ , since r is halved, v is halved;
$v=0.5\left(\mathrm{~ms}^{-1}\right) ;$

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IB Physics SL A 2 26 Angular and Linear Speed Questions question 1