DP Physics (first assessment 2025)

Question 23M.2.HL.TZ2.iii

Date	May 2023	Marks available	[Maximum mark: 2]	Reference code	23M.2.HL.TZ2.iii
Level	HL	Paper	2	Time zone	TZ2
Command term	Calculate	Question number	iii	Adapted from	N/A

iii.

[Maximum mark: 2]

23M.2.HL.TZ2.iii

When the spheres move outward, the angular speed decreases from 20 rad s⁻¹ to 12 rad s⁻¹. Calculate the percentage change in rotational kinetic energy that occurs when the spheres move outward.

[2]

Markscheme

«E_k =» $\frac{1}{2}$ Lω₁ = $\frac{1}{2}$ Lω₂ ✓

$\frac{E_{k 1}}{E_{k 2}} = \frac{ω_{1}}{ω_{2}}$

«L is constant so» E_k is proportional to ω ✓

40 % «energy loss» ✓

MP1 is for understanding that angular momentum is constant so change in rotational kinetic energy is proportional to change in angular velocity

Award [0] if E = 0.5 I ω² is used with the same I value for both values of E

Award [2] for BCA

Syllabus sections

A. Space, time and motion » A.4 Rigid body mechanics

Question 23M.2.HL.TZ2.iii

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