DP Physics (last assessment 2024)

Question 20N.2.HL.TZ0.7a

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.2.HL.TZ0.7a
Level	HL	Paper	2	Time zone	TZ0
Command term	Outline	Question number	a	Adapted from	N/A

[Maximum mark: 1]

20N.2.HL.TZ0.7a

A vertical solid cylinder of uniform cross-sectional area $A$ floats in water. The cylinder is partially submerged. When the cylinder floats at rest, a mark is aligned with the water surface. The cylinder is pushed vertically downwards so that the mark is a distance $x$ below the water surface.

At time $t = 0$ the cylinder is released. The resultant vertical force $F$ on the cylinder is related to the displacement $x$ of the mark by

$F = - ρ A g x$

where $ρ$ is the density of water.

(a)

Outline why the cylinder performs simple harmonic motion when released.

[1]

Markscheme

the «restoring» force/acceleration is proportional to displacement ✓

Allow use of symbols i.e. $F \propto - x$ or $a \propto - x$

Examiners report

This was well answered with candidates gaining credit for answers in words or symbols.