Download Interactions specimen questions

17. In reactions between sub-nuclear particles, various numbers have been found to be conserved
(i.e. unchanged throughout a reaction).
(a) State whether or not the following numbers are conserved:
Number
Baryon
Meson
Lepton
Conserved (Yes / No)
[3]
(b) The following decay is observed to occur:
p
n +  + + e
(i) State this equation in words:
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
[2]
(ii) State three conservation laws that this decay demonstrates.
1..................................................................................................................................................
2..................................................................................................................................................
3..................................................................................................................................................
[3]
(c) This reaction cannot occur:
p + e
n + e
Which conservation law does it break?
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....................................................................................................................................................
[1]
Total 9 marks
18. Physicists are attempting to find a unified theory of the fundamental forces of nature.
(a) Name the four forces involved.
....................................................................................................................................................
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....................................................................................................................................................
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[4]
(b) State the force involved in:
(i) holding quarks together in a proton.
....................................................................................................................................................
[1]


(ii)  decay of a proton.
....................................................................................................................................................
[1]


(iii)  particle scattering by a nucleus.
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[1]
(c) These forces are described by the exchange of particles. Name two of the exchange
particles involved in the situations listed in b).
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[2]
Total 9 marks
19. A bubble chamber is used to observe the tracks of particles formed by collision reactions. A
researcher drew the following sketch from a bubble chamber photograph.
P
There is a magnetic field acting downwards into the plane of the diagram.
The reactions that took place were:
p
n +  + + e
followed by:
n
p +  - + e
(a) Label each of the tracks in the boxes on the sketch with the symbol of the particle it
represents.
[5]
(b) Explain why some of the particle tracks are shown as dashed lines.
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[3]
Total 8 marks
17.(a)
Number
Baryon
Meson
Lepton
Conserved (Yes / No)

Yes

No

Yes
[3]


(b) (i) proton decays to: neutron + positron (positive beta) + (electron) neutrino
[2]

(ii) Conserved quantities are: Baryon number (p goes to n)

Lepton number (zero goes to + (anti lepton) + e)
charge (total +1 both sides). 
[3]
(c) Lepton number not conserved ( e- goes to e (anti-neutrino)) 
[1]
Total 9 marks
18.(a) The four forces are: gravitational, electromagnetic, strong nuclear , weak nuclear
(electromagnetic and weak can be combined as electroweak)
[4]
(b) (i) strong 
(ii) weak 
(iii) electromagnetic (electrostatic) 
[3]
(c) Any two of: gluon, W-boson, photon.  
[2]
Total 9 marks
19.(a) The particle tracks are:
 p

 +

e
n
-

p
Note the charge on the particles can be found from the direction in which they curve in
the magnetic field. Faster moving particles have more curved paths.
[5]

(b) The dashed tracks indicate uncharged particles (neutron and neutrinos)
 trails in the bubble chamber
Uncharged particles produce no ionisation
Their paths are inferred from the tracks that are visible.

[3]
Total 8 marks