DP Physics (first assessment 2025)

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Question 19M.2.HL.TZ1.a.i

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Date May 2019 Marks available [Maximum mark: 3] Reference code 19M.2.HL.TZ1.a.i
Level HL Paper 2 Time zone TZ1
Command term Show that Question number a.i Adapted from N/A
a.i.
[Maximum mark: 3]
19M.2.HL.TZ1.a.i

Show that the angular acceleration  a of the cylinder is g 3 R

[3]

Markscheme

equations of motion are: TR = 1 2 MR2  a  and  M g 4  − T =  M 4 a

OR

M 4 gR =  1 2 MR2  a  +  M 4 Ra

use of a = a R ✔

combine equations to get result ✔

Allow energy conservation use.

This is a show that question, so look for correct working.

Do not allow direct use of tension from a ii)

Examiners report

This simple system of a solid cylinder rotating about a fixed axle and a block hanging on the rope accelerating proved to be rather difficult for many candidates. Only the best candidates were able to solve this problem, by writing two separate equations, and then solving to establish the acceleration of the system. The use of energy conservation was not a common technique attempted by students. As this is a “show that” question, candidates were asked to show that the angular acceleration is equal to g/(3R). Quite a high number of candidates successfully used the equations of motion and a similar number used the moment of inertia of the block around the axle. 

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