Question

27) If F = 2i +3j-k and r =i-j+6k find r*F​

Answer 1

Answer:

- 7

Explanation:

product of force and displacement gives workdone( scalar), so it is scalar product. In this,

i^2 = 1,  j^2 = 1,  k^2 = 1.  

And, remaining all, like i.j, i.k, k.i, etc are 0. So multiply with same constants only.

⇒ F.r

⇒ (2i + 3j - k)(i - j + 6k)

⇒ 2(i^2) - 3(j^2) - 6(k^2)

⇒ 2(1) - 3(1) - 6(1)

⇒ 2 - 3 - 6

⇒ - 7