Steven W. answered • 10/16/16
Tutor
4.9
(4,315)
Physics Ph.D., college instructor (calc- and algebra-based)
Hi Porcia!
Based on what I see, I am guessing you ended up with:
y - 4 = -60.175
I think your only error is that you mistakenly subtracted 4 from -60.175 instead of adding it. Just a very common mistake (that I have made very often). So I think your answer should be -56.175. Other than that, you were right on, so great work!
Steven W.
tutor
It looked like you computed the angle correctly in (a), so -- once you have the correct components for both x and y -- identify which is opposite and which is adjacent with respect to an angle measured from the +x axis to the resultant. Then compute the angle using the standard opposite/adjacent formula, just as you appear to have done correctly before. See if that works!
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10/16/16
Porcia C.
I tried. Physics just puzzles me lol I'm so. Lost
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10/16/16
Steven W.
tutor
Well, it looks like you are getting a lot of it correct. Your only error above was mathematical.
So, the x component of its position is (+)365.7, as you correctly determined
The y component, which you almost correctly determined, is -56.175.
So the position must be in the 4th quadrant. If you look at a right triangle with those components as the legs, the hypotenuse points into the 4th quadrant, and the angle it makes with the +x axis is such that the y component is opposite the angle, and the x component is adjacent.
So, you can compute the smallest angle between the +x axis and the position vector by using
tan(θ) = (56.175)/(365.69) --> θ = tan-1(56.175/365.69) = 8.73°
And this is BELOW the +x axis, or, in other words, measured clockwise from it. To get the corresponding counterclockwise angle, we would have to imagine starting at the +x axis, and swing all the way around into the 4th quadrant to match up with the vector. You may be able to see that this counterclockwise angle is just 360° - 8.73° = 351.27°.
You can think of this as, we swing all the way around counterclockwise, and then back up clockwise by the 8.73° we calculated above to line with the position vector.
Keep the questions coming if you are still lost in any way!
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10/16/16
Porcia C.
It says that answer wrong
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10/16/16
Steven W.
tutor
Hmmm, that is from the +x axis counterclockwise. It said your answer of -31.55 for the acceleration direction above was correct. So maybe try -8.73.
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10/16/16
Porcia C.
still wrong
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10/16/16
Steven W.
tutor
Then, for the moment, I am a bit flummoxed, because (except for that math error), I agree with your numbers. I will look at it again when I get home.
Could it possibly be a significant figures issue?
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10/16/16
Steven W.
tutor
No, I still get the y-direction position is -56.175, and then the same value for the angle: 8.73 degrees below the +x axis. and thus 351.27 measured counterclockwise.
The only thing I can think of is that it needs fewer significant figures or something. But, in terms of calculation, I cannot find anything wrong with it, especially given that your components of acceleration are right on.
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10/16/16
Porcia C.
10/16/16