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Question 18N.2.HL.TZ0.3

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Date November 2018 Marks available [Maximum mark: 8] Reference code 18N.2.HL.TZ0.3
Level HL Paper 2 Time zone TZ0
Command term Define, Determine, Explain, Show that Question number 3 Adapted from N/A
3.
[Maximum mark: 8]
18N.2.HL.TZ0.3
(a)

Define impulse.

[1]

Markscheme

force × time

OR

change in momentum ✔

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.

(b.i)

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

[1]

Markscheme

Ek = 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.ii)

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]

Markscheme

ALTERNATIVE 1:

initial momentum = mv =  2 × 0.058 × 0.63  «= 0.27 kg m s−1»

OR

mv =  0.058 × 2 × 9.81 × 1.1  «= 0.27 kg m s−1» ✔

force = « change in momentum time =»  0.27 0.055  ✔

4.9 «N» ✔

F − mg = 4.9 so F = 5.5 «N» ✔

 

ALTERNATIVE 2:

«Ek = 1 2 mv2 = 0.63 J» v = 4.7 m s−1 ✔

acceleration = « Δ v Δ t =»  4.7 55 × 10 − 3 = «85 m s−2» ✔

4.9 «N» ✔

F − mg = 4.9 so F= 5.5 «N» ✔

 

Accept negative acceleration and force.

(b.iii)

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

[2]

Markscheme

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.

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