(a) Sand dunes on a desert island move as sand is swept up the windward side to settle in the leeward side. Such "walking" dunes have been known to travel 18 feet in a year and can travel as much as 100 feet per year in particularly windy times. Calculate the average speed in each case in m/s.

the two that i'm getting wrong are
18ft/y
and
100ft/y

this is how i solved the first one...

(18ft/yr)(12in/1ft)(2.54cm/1in)(1m/100cm)(1yr/365days)(1day/3600sec)= 4.17E-6
and it says "Your answer differs from the correct answer by orders of magnitude. m/s"
i changed my answer to 4.17E6 but it says the same thing... does it have to do with scientific notation, i have no idea.

1/11/2008 4:14:50 PM

im assuming it wants you to round to the nearest power of 10, but i could be wrong

1/11/2008 4:46:41 PM

First, convert your feet to meters:

18 feet = 5.4864 meters
100 feet = 30.48 meters

Second, convert your years to seconds:

1 year = 365 days = 31 536 000 seconds


Last, simply form the ratio of meters/seconds for the appropriate measurement.
For example: 5.00 meters / 31536000 seconds = 1.58E-7


You are indeed off by an order of magnitude, using the conversions above you will find your answer to be on the order of E-7 (The answer should be negative).

[Edited on January 11, 2008 at 4:54 PM. Reason : .]

1/11/2008 4:49:00 PM

^thank you
looks a lot simpler than w/e i was trying to do

1/11/2008 5:18:57 PM

bdxzok, your method was correct. However, there are 24*3600 seconds in a day. You had the number of seconds in an hour.

1/11/2008 5:42:57 PM

haha i see now. stupid mistakes as usual

1/11/2008 7:11:09 PM