DP Physics (first assessment 2025)

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Question 22N.2.SL.TZ0.6b.ii

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Date November 2022 Marks available [Maximum mark: 3] Reference code 22N.2.SL.TZ0.6b.ii
Level SL Paper 2 Time zone TZ0
Command term Show Question number b.ii Adapted from N/A
b.ii.
[Maximum mark: 3]
22N.2.SL.TZ0.6b.ii
(b.ii)

The polonium nucleus was stationary before the decay.

Show, by reference to the momentum of the particles, that the kinetic energy of the alpha particle is much greater than the kinetic energy of the lead nucleus.

[3]

Markscheme

ALTERNATIVE 1

energy ratio expressed in terms of momentum, e.g. EαElead=pα2/2mαplead2/2mlead ✓

pα=plead hence EαElead=mleadmα ✓

 

mleadmα≃2064=51.5⇒Eα=51.5Elead  «so α has a much greater KE»

OR

mlead «much» greater than malpha «so α has a much greater KE» ✓

 

ALTERNATIVE 2

alpha particle and lead particle have equal and opposite momenta ✓

so their velocities are inversely proportional to mass ✓

but KE ∝ v2 «so α has a much greater KE» ✓

Examiners report

Those who answered using the mass often did not get MP3 whereas those who converted to the number of particles or moles before the first calculation did, although that could be considered an unnecessary complication.

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