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Question 19M.2.HL.TZ1.6c.ii

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Date May 2019 Marks available [Maximum mark: 2] Reference code 19M.2.HL.TZ1.6c.ii
Level HL Paper 2 Time zone TZ1
Command term Calculate Question number c.ii Adapted from N/A
c.ii.
[Maximum mark: 2]
19M.2.HL.TZ1.6c.ii
(c.ii)

Calculate, for the cylinder, at the instant just before the block hits the ground the kinetic energy.

[2]

Markscheme

ω =< a Δt = g 3 R  Δt = 9.81 × 0.55 3 × 0.20 = > 8.99 «rads−1» ✔

Ek = « 1 2 Iω2 =  1 4 MR2 ω2 =  1 4  × 12 × 0.202 × 8.992 = » 9.7 «J» 

Award [2] for a bald correct answer.

Examiners report

Angular speed, angular momentum and the kinetic energy of the cylinder at the instant given were successfully calculated by only the better-prepared candidates. Students were mostly able to recognize the correct expressions to use but struggled to find the angular speed in many instances. Error carried forward was very common throughout this question for students who incorrectly determined the angular velocity but understood and correctly applied the momentum and energy equations. In ii), quite a high number of candidates misread the question and calculated the energy of the whole system.

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