DP Physics (last assessment 2024)

Question 17N.3.HL.TZ0.7a

Date	November 2017	Marks available	[Maximum mark: 4]	Reference code	17N.3.HL.TZ0.7a
Level	HL	Paper	3	Time zone	TZ0
Command term	Determine	Question number	a	Adapted from	N/A

[Maximum mark: 4]

17N.3.HL.TZ0.7a

The ${\Lambda ^0}$ (Lambda) particle decays spontaneously into a proton and a negatively charged pion of rest mass 140 MeV c^–2. After the decay, the particles are moving in the same direction with a proton momentum of 630 MeV c^–1 and a pion momentum of 270 MeV c^–1.

(a)

Determine the rest mass of the ${\Lambda ^0}$ particle.

[4]

Markscheme

$\Lambda$ momentum = 900

E_proton = « $\sqrt {p{c^2} + {{\left( {m{c^2}} \right)}^2}} = \sqrt {{{630}^2} + {{938}^2}} =$ » 1130 «MeV»

E_pion = « $\sqrt {{{270}^2} + {{140}^2}} =$ » 304 «MeV»

so rest mass of $\Lambda$ = « $\sqrt {{{\left( {1130 + 304} \right)}^2} - {{900}^2}} =$ » 1116 «MeV c^–2»

Syllabus sections

Option A: Relativity

Option A: Relativity » Option A: Relativity (Additional higher level option topics) » A.4 – Relativistic mechanics (HL only)

Option A: Relativity » Option A: Relativity (Additional higher level option topics)

Question 17N.3.HL.TZ0.7a

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