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phy131studiof16:lectures:chapter3b [2016/09/12 08:53]
mdawber [Relative Velocity with Vector Sums]
phy131studiof16:lectures:chapter3b [2016/09/12 09:22] (current)
mdawber [Crossing a river]
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 We need to draw the diagram using the known angles to set up the problem to find the speed the swimmer should maintain. We need to draw the diagram using the known angles to set up the problem to find the speed the swimmer should maintain.
 +
 +===== Problem 3.70 - the problem I meant to assign instead of 3.7 =====
 +
 +Relative to the water, the boat has a known velocity $v_{BW}$ (including direction $\theta_{BW}$). ​
 +
 +The direction of the boat's velocity relative to the land can be deduced as $\tan\theta_{BL}=\frac{120\mathrm{m}}{280\mathrm{m}}$. ​
 +
 +{{3_70_1.png}}
 +
 +
 +===== Problem 3.70 solution =====
 +
 +
 +
 +|{{3_70_2_sine.png}}| Use the sine rule. \\ $\frac{v_{WL}}{sin(\theta_{BW}-\theta_{BL})}=\frac{v_{BW}}{sin(90^{o}+\theta_{BL})}=\frac{v_{BL}}{\sin(90^{o}-\theta_{BW})}$ |
 +|{{3_70_2_components.png}}| or use components. \\ $\frac{v_{BW}\sin\theta_{BW}-v_{WL}}{v_{BW}\cos\theta_{BW}}=\tan\theta_{BL}$. |
 +
 +(Recall that $\tan\theta_{BL}=\frac{120\mathrm{m}}{280\mathrm{m}}$).
phy131studiof16/lectures/chapter3b.txt ยท Last modified: 2016/09/12 09:22 by mdawber
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