Let
#"East"-> +"ve direction of x-axis"#
#"West"->-"ve direction of x-axis"#
#"North"-> +"ve direction of y-axis"#
#"South"->-"ve direction of y-axis"#
#vec(V_i)->"Initial velocity vetor"#
#vec(V_f)->"Final velocity vetor"#
#abs(vec(V_i))=8.5m/s#
#abs(vec(V_f))=19m/s#
#t->"Time of change of velocity"=2s#
#"Direction of "vec(V_i)=S42^@W=(270-42)^@#
#"Direction of "vec(V_f)=W35^@N=(180-35)^@#
#vec(V_i)=8.5(cos(270-42)hati+sin(270-42)hatj)#
#=-8.5(sin42hati+cos42hatj)#
#=-5.69hati-6.32hatjm/s#
#vec(V_f)=19(cos(180-35)hati+sin(180-35)hatj)#
#=19(-cos35hati+sin35hatj)#
#=-15,56hati+10.9hatjm/s#
#"Now average acceleration"#
#vec(a)=(vec(V_f)-vec(V_i))/t#
#=1/2(-9.87hati+17.22hatj)ms^-2#
#abs(vec(a))=1/2sqrt(9.87^2+17.22^2)~~19.85ms^-2#
