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Physics 20 Online
OpenStudy (anonymous):

Suppose you walk 15 m in a direction exactly 25° south of west then you walk 22.5 m in a direction exactly 45° west of north. What is the angle of the compass direction of a line connecting your starting point to your final position measured South of West in degrees? Repeat part (a) by finding your distance from the starting point in m, but reverse the order of the two legs of the walk. That is, you first walk leg B, which is 22.5 m in a direction exactly 45° west of north, and then leg A, which is 15 in a direction exactly 25° south of west. What is the angle of the compass direction o

OpenStudy (anonymous):

*What is the angle of the compass direction of a line connecting your starting point to your final position measured South of West in degrees?

OpenStudy (roadjester):

I keep getting an angle of either 342 degrees or 162 degrees, one of which is east of south and the other is west of north... @LastDayWork

OpenStudy (roadjester):

OOH, I know what I screwed up on. Ok @jhc2014 are you familiar with vectors/ vector components?

OpenStudy (lastdaywork):

Write the two steps as vectors (in polar form).

OpenStudy (anonymous):

not to familiar and not sure what polar form is

OpenStudy (roadjester):

|dw:1392271434007:dw|

OpenStudy (anonymous):

how would you get the angle of the compass from that? what formula would you have to use

OpenStudy (roadjester):

ok, you'll have to break the vectors into their x and y components

OpenStudy (anonymous):

that be 22.5cos(45)+15cos(25) for x right and 22.5sin(45)+15sin(25) for y right ?

OpenStudy (roadjester):

you're VERY close

OpenStudy (roadjester):

ok, first, for the x-axis, if you're right of the y-axis, then your numbers are positive, if you're on the left, the numbers are negative second, the angles 25 and 45 that you're given are relative. you have to start from the horizontal for your angles. so for example, the first vector that is "25". That starts from the negative x-axis. You need to add 180 so that you start from the positive x-axis. So the two questions you need to ask are: Is the vector component positive or negative? How do I modify the angles so that they include the FULL angle?

OpenStudy (roadjester):

In my explanation, I didn't include the y-component. I want to see if you can figure that out.

OpenStudy (anonymous):

y component=22.5sin(45)+15sin(205)?

OpenStudy (roadjester):

-15 sin(205) +22.5 sin (90 + 45)

OpenStudy (roadjester):

good attempt though. Does that make sense?

OpenStudy (anonymous):

yes the angle is the vector itself right

OpenStudy (roadjester):

ok so now you have your x and y to get your new angle tan^-1 (y/x)

OpenStudy (anonymous):

41.7 degrees

OpenStudy (anonymous):

never mind i made a calculation error -84.1 degrees?

OpenStudy (roadjester):

x-component: 29.505 y=component 22.249

OpenStudy (roadjester):

Your components are off

OpenStudy (anonymous):

37.01905419 my x component was wrong

OpenStudy (anonymous):

having the angle how would you find the distance from the starting point in meters but reverse the order of the two legs of the walk. That is, you first walk leg B, which is 22.5 m in a direction exactly 45° west of north, and then leg A, which is 15 in a direction exactly 25° south of west.?

OpenStudy (roadjester):

use the pythagorean theorem

OpenStudy (anonymous):

you should get 36.95 right

OpenStudy (roadjester):

yes

OpenStudy (anonymous):

when i went to put it in it said it was wrong

OpenStudy (roadjester):

in what?

OpenStudy (anonymous):

my online homework site

OpenStudy (roadjester):

were ALL the answers wrong?

OpenStudy (anonymous):

no the other ones were right

OpenStudy (roadjester):

so just the length of the reverse?

OpenStudy (anonymous):

yes

OpenStudy (roadjester):

is this due immediately? I'm trying to figure out what we did wrong...

OpenStudy (anonymous):

no not immediately

OpenStudy (anonymous):

to be honest i have no idea why the Pythagorean therom didnt work

OpenStudy (roadjester):

maybe sig figs?

OpenStudy (anonymous):

i tried sigfigs but used my last attempt and the right answer was 31.02 so we were really close but i appreciate all the help youve given me wouldnt have been able to get it done without you thank you

OpenStudy (roadjester):

oh, you only had a fixed number of tries?? I'm sorry

OpenStudy (anonymous):

its not problem still got the others right no problem at all thanks again

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