# Physics

What is the magnitude of the resultant velocity for a bird flying first at a speed of 10m/s North East and then flying to south at a speed of 8m/s?

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1. Draw the vectors. All you need here is the 3rd side of the triangle.
Use the law of cosines.
x^2 = 10^2 + 8^2 - 2*10*8*cos45°

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2. Va=10cos45 E + 10 sin45 N
Vb=-8N

VresultN=Va+Vb=10*.707-8 N=7.07-8 N= .93S
Vreslt= Vn + 10*.707E
magnitude= sqrt(.93^2 + 7.07^2)

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bobpursley
3. All angles are measured CW from +y-axis.
Vr = 10m/s[45o] + 8m/s[180o].

X = 10*sin45 + 8*sin180 = 7.07 m/s.
Y = 10*Cos45 + 8*Cos180 = -0.93 m/s.

Vr = sqrt(X^2+Y^2).

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4. 7.13

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