Final Displacement

  • #1
1. A cyclist rides 3.0 km due west, then 16.0 km 23° west of north. From this point she rides 9.0 km due east. What is the final displacement from where the cyclist started (in km)? (Express your answer in vector form. Assume the +x-axis is to the east, and the +y-axis is to the north.)

Picture of question: https://gyazo.com/31eff7abeed1f8ef80293518c12f183b



2. Displacement = r final - r initial


3. I converted the cardinal coordinates to (3, 180 degrees), (16, 113 degrees), and (9,0 degrees). The total of the vectors in vector form is -0.25i + 14.7j. That's the displacement if the origin is (0,0) by my estimation, but that answer was rejected. What am I missing?
 

Answers and Replies

  • #2
verty
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Try 14.73 for the ##\hat{j}## component. Otherwise I get the same answers.
 
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  • #3
PeroK
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1. A cyclist rides 3.0 km due west, then 16.0 km 23° west of north. From this point she rides 9.0 km due east. What is the final displacement from where the cyclist started (in km)? (Express your answer in vector form. Assume the +x-axis is to the east, and the +y-axis is to the north.)

Picture of question: https://gyazo.com/31eff7abeed1f8ef80293518c12f183b



2. Displacement = r final - r initial


3. I converted the cardinal coordinates to (3, 180 degrees), (16, 113 degrees), and (9,0 degrees). The total of the vectors in vector form is -0.25i + 14.7j. That's the displacement if the origin is (0,0) by my estimation, but that answer was rejected. What am I missing?
Your answer looks good to me.
 
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  • #4
Try 14.73 for the ##\hat{j}## component. Otherwise I get the same answers.
Thank you for your reply. Apparently, I entered -0.26i as my initial answer and it rejected that. Usually if the answer is close, it accepts it. Their criteria for solutions is frustrating.
 
  • #5
Your answer looks good to me.
As I mentioned to verty, after I increased -0.26i to -0.25i, it accepted by answer. I wasted an hour of my life on one question. :sorry:
 

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