Assume two vectors u=xi^+yj^+zk^,v=ai^+bj^+ck^ .
Now, u.v=(xi^+yj^+zk^).(ai^+bj^+ck^)=xa+yb+zc ...(i)
And v.w=(ai^+bj^+ck^).(xi^+yj^+zk^)=ax+by+cz ...(ii)
From (i) and (ii), u.v=v.u
Hence, commutative.
Also, assume another vector w=pi^+qj^+rk^
(u.v).w=[(xi^+yj^+zk^).(ai^+bj^+ck^)].(pi^+qj^+rk^)=[xa+yb+zc].(pi^+qj^+rk^)
which is not defined as dot product of a scalar and vector quantity is not defined.
Now,
u.(v.w)=(xi^+yj^+zk^).[(ai^+bj^+ck^).(pi^+qj^+rk^)]=(xi^+yj^+zk^).(ap+bq+cr)
which is not defined as dot product of a scalar and vector quantity is not defined.
Hence, not associative.
Comments