⃗ F = 3 ^ i + 6 ^ j − 8 ^ k ⃗ s = − 2 ^ i + 5 ^ j + 2 ^ k If W = ⃗ F . ⃗ s find W. Options: A . &nbsp 8 N. m B . &nbsp 20 N. m C . &nbsp 5 N. m D . &nbsp None of these

⃗F=3^i+6^j−8^k ⃗s=−2^i+5^j+2^k If W =⃗F.&

Question -

$⃗ F = 3^i + 6^j - 8^k$

$⃗ s = - 2^i + 5^j + 2^k$

If W = $⃗ F . ⃗ s$ find W.

Options:

A . 8 N. m

B . 20 N. m

C . 5 N. m

D . None of these

Answer: Option A
:
A

$⃗ F = 3^i + 6^j - 8^k$

$⃗ s = - 2^i + 5^j + 2^k$

W = $⃗ F . ⃗ s$

= $(3^i + 6^j - 8^k) . (- 2^i + 5^j + 2^k)$

= (-6) + (30) + (-16)

$∵ (^i .^i = 1 &^i .^j = 0)$

W = 8 N.m

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