Direction of Displacement Vector [2D Kinematics]

AI Thread Summary
The discussion focuses on solving a 2D kinematics problem involving displacement vectors. The first question is correctly solved, with the resultant displacement calculated as 20.1 km. For the second question, participants discuss the correct approach to find the direction of the displacement vector using trigonometric functions, specifically the arctangent. There is confusion regarding the counter-clockwise angular direction and its limits, prompting suggestions to visualize the problem on a Cartesian plane. The conversation emphasizes using the Pythagorean theorem and trigonometric identities to clarify the solution process.
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Homework Statement



Question 1 [Correctly Solved]
A pedestrian moves 2.1km east and then 20km north. Find the magnitude of the resultant displacement vector. Answer in units of km.

Answer = 20.1km

Question 2
What is the direction of the displacement vector (using the counter-clockwise angular direction to be positive, within the limits of -180 degrees = 180 degrees)? Answer in units of degrees/

The Attempt at a Solution



[Theta] = (arctan) (Ay/Ax)
[Theta] = (arctan) 20km/2.1km = 1.466

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I'm probably using the wrong equation. :x
(using the counter-clockwise angular direction to be positive, within the limits of -180 degrees = 180 degrees) Also, I don't understand what that means. Will someone please explain? :blushing:
 
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question #1: Draw it on a sheet of paper, make a Cartesian plane, use the upper y-axis as north, right x-axis as east. You ll remember something!
*hint* Pythagorean Theorem ;)

Question #2: now I am not sure if ill explain this right but! i think that this : "using the counter-clockwise angular direction to be positive, within the limits of -180 degrees = 180 degrees" means find the angle opposite to the 20km line (i think its the angle between the hypotenus and the 2.1km line)
Let's say it is ;)
now remember SOHCAHTOA and see if you can do it.

Got more questions, just PM me. Goodluck!
 
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