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March 3, 2015

March 3, 2015

Posted by **Anonymous** on Tuesday, February 26, 2008 at 7:35pm.

Suppose that the boat is supposed to arrive at a point directly across the river from its starting point.

a) What should be the heading of the boat?

- Physics continuation - Damon please help -
**Lance**, Tuesday, February 26, 2008 at 7:48pmThere is not enough information, was there a previous question or other info?

- Physics continuation - Damon please help -
**Damon**, Tuesday, February 26, 2008 at 7:56pmThe river flowed at 10 km/hr

the boat went at 24 km/hr

The boat must head upstream such that 24 sin T = 10

or T = 24.6 degrees upstream of straight across

By the way, his speed across the river is now 24 cos 24.6 degrees = 21.8 km/hr

- Physics continuation - Damon please help -
**Damon**, Tuesday, February 26, 2008 at 8:02pmBy the way, this is why you swim aiming toward the other bank and let yourself be swept downstream. If you try to head enough upstream to make a path straight across to a selected spot on the other bank, you will take longer getting across assuming you do not mind landing downstream on the other bank.

In the limit, as the current reaches your swimming speed, you will never reach the other side, whereas if you just aim for the other bank and let the current take you as it wishes, at least you will get to the other side if somewhat downstream.

- Physics continuation - Damon please help -
**Anonymous**, Tuesday, February 26, 2008 at 8:05pmThe answer says 65 degrees upstream. I don't know how they got that.

- Physics continuation - Damon please help -
**Damon**, Tuesday, February 26, 2008 at 8:09pmWell, I did 24.6, call it 25 degrees from straight across.

That is 90 - 25 = 65 degrees from the bank.

I think the question was designed by a mathematician, not a navigator :)

- Physics continuation - Damon please help -

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