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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] Both sides previous revision Previous revision 2016/09/12 09:22 mdawber [Crossing a river] 2016/09/12 08:53 mdawber [Relative Velocity with Vector Sums] 2016/09/12 08:44 mdawber [Chapter 3 - Relative velocity and other 2 vector problems] 2016/09/11 21:48 mdawber [Before we move on from projectiles] 2016/09/11 21:45 mdawber [Before we move on from projectiles] 2016/09/11 21:45 mdawber [Chapter 3 - Relative velocity and other 2 vector problems] 2016/09/11 21:31 mdawber [Canoe on a river] 2016/09/11 21:21 mdawber [Canoe on a river] 2016/09/11 21:21 mdawber [Canoe on a river] 2016/09/11 21:20 mdawber [Solution for relative velocity example] 2016/09/11 21:13 mdawber [Some problems involving finding velocity in a moving reference frame] 2016/09/11 21:10 mdawber [Relative velocity example] 2016/09/11 21:10 mdawber [Problem 3.58] 2016/09/11 21:07 mdawber [Using Relative Velocity] 2016/09/11 21:05 mdawber [Relative Velocity with Vector Sums] 2016/09/11 21:04 mdawber [Relative velocity example] 2016/09/11 21:02 mdawber [Chapter 3 - Relative velocity and other 2 vector problems] 2016/09/11 21:01 mdawber [Relative Velocity] 2016/07/28 13:42 mdawber 2016/07/28 13:23 mdawber created 2016/09/12 09:22 mdawber [Crossing a river] 2016/09/12 08:53 mdawber [Relative Velocity with Vector Sums] 2016/09/12 08:44 mdawber [Chapter 3 - Relative velocity and other 2 vector problems] 2016/09/11 21:48 mdawber [Before we move on from projectiles] 2016/09/11 21:45 mdawber [Before we move on from projectiles] 2016/09/11 21:45 mdawber [Chapter 3 - Relative velocity and other 2 vector problems] 2016/09/11 21:31 mdawber [Canoe on a river] 2016/09/11 21:21 mdawber [Canoe on a river] 2016/09/11 21:21 mdawber [Canoe on a river] 2016/09/11 21:20 mdawber [Solution for relative velocity example] 2016/09/11 21:13 mdawber [Some problems involving finding velocity in a moving reference frame] 2016/09/11 21:10 mdawber [Relative velocity example] 2016/09/11 21:10 mdawber [Problem 3.58] 2016/09/11 21:07 mdawber [Using Relative Velocity] 2016/09/11 21:05 mdawber [Relative Velocity with Vector Sums] 2016/09/11 21:04 mdawber [Relative velocity example] 2016/09/11 21:02 mdawber [Chapter 3 - Relative velocity and other 2 vector problems] 2016/09/11 21:01 mdawber [Relative Velocity] 2016/07/28 13:42 mdawber 2016/07/28 13:23 mdawber created Line 124: Line 124: 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 $\tan\theta_{BL}=\frac{120\mathrm{m}}{280\mathrm{m}}$). 