**ships in the night**
Hi folks,
The velocity of ship A relative to ship B is 10.0 km/h in a direction North 45 East. If the velocity of B is 20 km/h in a direction N 60 W, find the actual velocity of A in magnitude and direction.
The attachment shows my sketch.
Vector A relative to B (OA in the sketch) is $\underline{a} - \underline{b}$
Vector A is AB
Vector B is OB
so A relative to B = AB + BO or AB - OB
to calculate vector A I used the cosine rule
magnitude of $AB^2 = \underline{a^2} = 10^2 + 20^2 -2.10.20 \cos 105 $
$\underline{a}^2 = 603.53$
$\underline{a}= 24.6$
this is the wrong answer. Correct is 19.8
can't see where I am going wrong!
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Last edited by uxinox; Jul 25th 2018 at 12:01 PM.
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