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Question 20N.3.HL.TZ0.12c(i)

Date	November 2020	Marks available	[Maximum mark: 2]	Reference code	20N.3.HL.TZ0.12c(i)
Level	HL	Paper	3	Time zone	TZ0
Command term	Determine	Question number	c(i)	Adapted from	N/A

c(i).

[Maximum mark: 2]

20N.3.HL.TZ0.12c(i)

A sphere is dropped into a container of oil.
The following data are available.

Density of oil $= 915 kg m^{- 3}$
Viscosity of oil $= 37.9 \times 10^{- 3} Pas$
Volume of sphere $= 7.24 \times 10^{- 6} m^{3}$
Mass of sphere $= 12.6 g$

The sphere is now suspended from a spring so that the sphere is below the surface of the oil.

(c(i))

Determine the force exerted by the spring on the sphere when the sphere is at rest.

[2]

Markscheme

$F = m g - ρ V g$

OR

$F = (0.0126 \times 9.81) - (915 \times 7.24 \times 10^{- 6} \times 9.81)$ ✓

$F = 5.86 \times 10^{- 2} « N »$ ✓

Accept use of $g = 10$ leading to $F = 6.0 \times 10^{- 2} N$

Examiners report

Continuing from b, most candidates scored full marks.

Syllabus sections

Option B: Engineering physics

Option B: Engineering physics » Option B: Engineering physics (Additional higher level option topics) » B.3 – Fluids and fluid dynamics (HL only)

Option B: Engineering physics » Option B: Engineering physics (Additional higher level option topics)