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Date	November 2018	Marks available	4	Reference code	18N.2.HL.TZ0.3
Level	Higher 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. Assume that air resistance is negligible and that the egg does not bounce or break.

Define impulse.

[1]

Show that the kinetic energy of the egg just before impact is about 0.6 J.

[1]

b.i.

The egg comes to rest in a time of 55 ms. Determine the magnitude of the average decelerating force that the ground exerts on the egg.

[4]

b.ii.

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

[2]

b.iii.

Markscheme

force × time

change in momentum ✔

E_k = mgh = 0.058 × 9.81 ×1.1 = 0.63 J ✔

Allow use of g = 10 m s⁻² (which gives 0.64 «J»)

Substitution and at least 2 SF must be shown

b.i.

ALTERNATIVE 1:

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

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» ✔

Accept negative acceleration and force.

b.ii.

ALTERNATIVE 1:

concrete reduces the stopping time/distance ✔

impulse/change in momentum same so force greater

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.iii.

Examiners report

[N/A]

b.i.

[N/A]

b.ii.

[N/A]

b.iii.

Syllabus sections

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

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