[" Two particles,"1" and "2" moves with constant velocity "vec V_(1)" and "vec V_(2)" .At the initial moment their radius vectors are "],[" equal to "vec r_(1)" and "vec r_(2)quad vec r_(1)=3hat i+2hat jmath],[" to collide "k=]

Two particles A and B, move with constant velocities vec(v_(1))" and "vec(v_(2)) . At the initial moment their position vectors are vec(r_(1))" and "vec(r_(2)) respectively. The condition for particle A and B for their collision is

Two particles A and B, move with constant velocities vec(v_(1))" and "vec(v_(2)) . At the initial moment their position vectors are vec(r_(1))" and "vec(r_(2)) respectively. The condition for particle A and B for their collision is

For any vector vec r ,prove that vec r=(vec r*hat i)hat i+(vec r*hat j)hat j+(vec r*hat k)hat k

For any vector vec r , prove that vec r=( vec r . hat i) hat i+( vec r . hat j) hat j+( vec r . hat k) hat kdot

The value of (vec r*hat i)(vec r xxhat i)+(vec r*hat j)(vec r xxhat j)+(vec r*hat k)(vec r xxhat k) is equal to '