# Thread: a man can swim at 1.4m/s in still water if he wishes to cross a river 180 m wide .. calculate (a) the time it will take

1. (b) the direction he should swim

2.

3. If the river Is Infested with Piranha he wouldn't make it to the other side at all.

4. c) do your own homework.

5. insufficient data to calculate direction.

6. And a good example of poor question found in many math textbooks. No mention of current..which all river's have and the other problem.

This is why kids show up in science courses without a clue how to solve problems, figure out what it's asking, what information is needed, or derive the right equations since they forgot the one they learned by rote and have now forgotten.
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The other problem imagine the question:

A car can travel at 120 mph. How long will it take a man to drive 110 miles from Portland, Maine to Boston.

7. Lynx

55 minutes of drive time
7 hours 14 minutes 39 seconds chatting with cops
so 8 hours 9 minutes 39 seconds(so far)
add in the court appearances to get his driving priveledges back including travel time for another 4 hours and 16 minutes
and we have a grand total of 12 hours 25 minutes and 39 seconds
or
we could just drive the speed limit say 65mph
and it would take 1 hour 45 minutes 33.36 seconds.

.........................

8. Originally Posted by Lynx_Fox
And a good example of poor question found in many math textbooks. No mention of current..which all river's have and the other problem.

This is why kids show up in science courses without a clue how to solve problems, figure out what it's asking, what information is needed, or derive the right equations since they forgot the one they learned by rote and have now forgotten.
My Calculus textbook in college contained the claim in the chapter on sinusoids, that pistons in an engine move in Simple Harmonic Motion (SHM), that is, sinusoidally. That is absolutely NOT the case. Just an example.

I have found in later life, that I can much more easily understand and work with some of the tough concepts from back in college days, by somehow viewing terms in practical perspective. Why, I don't know. Sure as hell, age has not made me smarter! For example: Back in Trigonometry, both high school and college, I simply could not comprehend practically the problems involving a rotating part using trig. to identify locations around it's periphery of motion. Typically, a Ferris Wheel, rotating at given speed, diameter given, how high off the ground will a car starting from the bottom be after "x" seconds? I solved those types of "polar trig." problems using conventional non-trigonometric means, to pass the exams. For some reason, today it's clear as a bell to me! Go figure! joc

9. Just the phrase "text book" is enough to give me pause.
Being forced to take 100 and 200 level classes after i had been mostly taking graduate level seminars was the real eye opener.
Many textbooks are poorly written by the poorly informed and poorly motivated.