Quarks and Leptons – MCQs (set 3)

Quarks are thought to make up protons and neutrons. The 'up' quark has a charge of +2/3e; a 'down' quark has a charge of -1/3 e, where e is the elementary charge (+1.6 x 10^-19 C). How many up quarks and down quarks must a proton contain?

• 0 up quarks, 3 down quarks

• 2 up quarks, 1 down quark

• 1 up quark, 2 down quarks

• 1 up quark, 1 down quark

Hadrons can be classified into mesons and baryons. Which of the following statements is true?

• Mesons always consist of three quarks

• Mesons always include a quark and an antiquark

• Mesons are formed during beta decay

• Neutrons and protons are examples of mesons

Nucleus Q decays by emitting a β^- particle to form a nucleus R. The quark composition of one nucleon in Q is changed during the emission of the β^- particle. What is the corresponding change in quark composition from nucleus Q to nucleus R?

• no change

• up quark → down quark

• down quark → up quark

• down quark → strange quark

Pions are the lightest mesons. A negative pion (π⁻) has a mass of 2.48 x 10^-28 kg. Which of the following is the mass of the π⁻ in MeV/c²?

• 1.4 x 10⁸ MeV/c²

• 1.4 x 10² MeV/c²

• 4.7 x 10⁻⁷ MeV/c²

• 3.6 x 10^-24 MeV/c²

Which one of the following might not apply in interactions between sub-atomic particles?

• charge conservation

• energy conservation

• matter conservation

• momentum conservation

When high-speed hadrons collide in particle accelerators, a positive pion (π⁺) is an unstable particle produced. The π⁺ particle has a charge of +e. What is the quark combination of the π⁺ particle?

Which row in the table gives the correct quark combination for the named particle?

• A

• B

• C

• D

A positive kaon (K+) is a meson that includes a strange quark. Its structure could be:

A pion can decay to produce two leptons. Which one of the following is possible?

In a nucleus of tritium, ³H, how many down quarks are there?

• 5

• 4

• 3

• 2