Two vectors, r and s lie in the xy plane. Their magnitudes are 4.5 and 7.2 units
ID: 2130347 • Letter: T
Question
Two vectors, r and s lie in the xy plane. Their magnitudes are 4.5 and 7.2 units, respectively and their directions are 320 degrees and 85 degrees respectively, as measured counterclockwise from the positive x axis. What is the cross product?
My attempts so far:
r x s = rs(sin(theta)) = (4.5)(7.2)sin(125) = 26.5405 Incorrect (also tried -26.5405 for fun Incorrect)
r x s = rs(sin(theta)) = (4.5)(7.2)sin(90) = Incorrect
rcos(theta) = 4.5cos320 = 3.4472
rsin(theta) = 4.5sin320 = -2.89254
scos(theta) = 7.2 cos85 = 0.627521
ssin(theta) = 7.2 sin85 = 7.42165
r x s = (rx)(sy)-(ry)(sx) = (3.4472)(7.42165)-(-2.89254)(0.627521) = 27.399 Incorrect
What am I doing wrong???
Explanation / Answer
r= rcos(360-320)i - r sin(360-320)j=4.5 cos(40)i- 4.5 sin(40)j
r=3.44 i - 2.89 j...
s=s cos(85)i + s sin(85)j....
s=0.627 i+7.172 j...
r X s=26.48 37K cap i.e perpendicular to xy plane
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