Question

solve all the questions .☺

Answer 1

Ans: 41 :
Let the two vectors be A and B.
Scalar Product = A . B = 6 (given)
|A| = 3 units
|B| = 4 units

We know, that
cos a = A. B / |A| |B| = 6/(3*4) = 1/2
=> cos a = 1/2
=> a = 60°
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Ans: 42 : F = -i + 2j + 3k
S = 4k = 0i + 0 j +4k

We know, that
Work Done = F. S
=(-i + 2 j + 3k) .( 0i + 0j + 4k)
= -1 * 0 + 2* 0 + 3*4
=12 J
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Ans :4 3
F = 7i + 6 k
v = 3i + 4k
We know, that
Power = F. v
= (7i + 6k) . ( 3i + 4k)
= 7*3 + 6* 4
= 21 + 24
= 45 W.