Identify the type of fundamental interactions associated with the exchange particles in the table.

State why ${\pi ^ + }$ mesons are not considered to be elementary particles.

Identify the exchange particle associated with this decay.

Deduce that this decay conserves baryon number.

electromagnetic;

strong;

they are composed of more than one quark;

${W^ + }$;

u has a baryon number of $\frac{1}{3}$ and ${\rm{\bar d}}$ has a baryon number of $- \frac{1}{3}$ ;

${\mu ^ + }$ and ${v_\mu }$ both have a baryon number of 0;

(a)(i) was well answered.

(a)(ii) was well answered.

Most answers to (b)(ii) used quark baryon numbers of 1 etc, not $\frac{1}{3}$.