Question #420ec

1 Answer
Aug 14, 2017

Given

  • #vecp=hati+2hatj-2hatk#

  • #vecq=2hati-hatj+2hatk#

we are to find #vecm and vecn# satisfying conditions

  • (a) #vecm# is perpendicular to #vec p#

  • (b) #vecn# is parallel to #vec p#

  • (c) #vecm+vecn=vecq#

By condition (b)#vecn# is parallel to #vec p#

So

  • We can write
    #vecn=alpha*vecp#,where #alpha# is a constant.

#vecn=alphavecp=alphahati+2alphahatj-2alphahatk#

By condition (c)

#vecm+vecn=vecq#

#=>vecm=vecq-vecn#

#=>vecm=(2-alpha)hati-(1+2alpha)hatj+(2+2alpha)hatk#

Now by condition (a) #vecm# is perpendicular to #vec p#

So #vecm*vecp=0#

#=>1xx(2-alpha)-2(1+2alpha)-2(2+2alpha)=0#

#=>2-alpha-2-4alpha-4-4alpha=0#

#=>alpha=-4/9#

Now
#vecn=alphahati+2alphahatj-2alphahatk#

#=>vecn=-4/9hati-8/9hatj+8/9hatk#

and

#vecm=(2-alpha)hati-(1+2alpha)hatj+(2+2alpha)hatk#

#=>vecm=(2+4/9)hati-(1-8/9)hatj+(2-8/9)hatk#

#=>vecm=22/9hati-1/9hatj+10/9hatk#