Find the moment about the point $i + 2 j - k$ of a force represented by $3 i + k$ acting through the point $2 j - j + 3 k .$

- 3 i + 13 j + 9 k

No worries! We‘ve got your back. Try BYJU‘S free classes today!

3 i - 13 j - 9 k

No worries! We‘ve got your back. Try BYJU‘S free classes today!

3 i - 11 j - 9 k

No worries! We‘ve got your back. Try BYJU‘S free classes today!

- 3 i + 11 j + 9 k

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

Open in App

Solution

The correct option is C $- 3 i + 11 j + 9 k$
$F = 3 i + k$ point about which moment is to be taken is $i + 2 j - k .$
$∴ x = \to O P = P . V .$ of $P - P . V$ of O $= (2 j - j + 3 x) - (i + 2 j - k)$ or $r = i = 3 j + 4 k .$
Hence the moment is $r \times F = (i - 3 j + 4 k) \times (3 i + k)$
$= ∣ ∣ ∣ ∣ \begin{matrix} i & j & k 1 & - 3 & 4 3 & 0 & 1 \end{matrix} ∣ ∣ ∣ ∣ = - 3 i + 11 j + 9 k .$

Suggest Corrections

Similar questions

A particle moves from position vector r1=3i^+2j^-6k^ to position vector r2=14i^+13j^+9k^ under the action of force 4i^+j^ +3k^N.Find the work done.

(4 i + j + 3 k) N

r_{1} = 3 i + 2 j - 6 k

r_{2} = 14 i + 13 j + 9 k,

a = i - 2 j + 3 k, b = 3 i - 6 j + 9 k

a = - 2 i - 4 k, b = i - 2 j - k, c = i - 4 j + 3 k

3 ˆ i + 2 ˆ j + 9 ˆ k

ˆ i - 2 p ˆ j + 3 ˆ k

5 j + k

9 i - j + 2 k .

3 i - 2 j + k

Join BYJU'S Learning Program