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Date	November 2018	Marks available	4	Reference code	18N.2.SL.TZ0.3
Level	Standard level	Paper	Paper 2	Time zone	0 - no time zone
Command term	Determine	Question number	3	Adapted from	N/A

Question

A chicken’s egg of mass 58 g is dropped onto grass from a height of 1.1 m. The egg comes to rest in a time of 55 ms. Assume that air resistance is negligible and that the egg does not bounce or break.

Determine the magnitude of the average decelerating force that the ground exerts on the egg.

[4]

a.

Explain why the egg is likely to break when dropped onto concrete from the same height.

[2]

b.

Markscheme

ALTERNATIVE 1:

initial momentum = mv = $\sqrt {2 \times 0.058 \times 0.63}$ «= 0.27 kg m s⁻¹»

OR

mv = $0.058 \times \sqrt {2 \times 9.81 \times 1.1}$ «= 0.27 kg m s⁻¹» ✔

force = « $\frac{{{\text{change in momentum}}}}{{{\text{time}}}}$ =» $\frac{{0.27}}{{0.055}}$ ✔

4.9 «N» ✔

F − mg = 4.9 so F= 5.5 «N» ✔

ALTERNATIVE 2:

«E_k = $\frac{1}{2}$ mv² = 0.63 J» v = 4.7 m s⁻¹ ✔

acceleration = « $\frac{{\Delta v}}{{\Delta t}}$ =» $\frac{{4.7}}{{55 \times {{10}^{ - 3}}}}$ = «85 m s⁻²» ✔

4.9 «N» ✔

F − mg = 4.9 so F= 5.5 «N» ✔

a.

ALTERNATIVE 1:

concrete reduces the stopping time/distance ✔

impulse/change in momentum same so force greater

OR

work done same so force greater ✔

ALTERNATIVE 2:

concrete reduces the stopping time ✔

deceleration is greater so force is greater ✔

Allow reverse argument for grass.

b.

Examiners report

[N/A]

a.

[N/A]

b.

Syllabus sections

Core » Topic 2: Mechanics » 2.4 – Momentum and impulse

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