Giancoli 7th Edition textbook cover
Giancoli's Physics: Principles with Applications, 7th Edition
3
Kinematics in Two Dimensions; Vectors
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3-2 to 3-4: Vector Addition
3-5 and 3-6: Projectile Motion
3-8: Relative Velocity

Question by Giancoli, Douglas C., Physics: Principles with Applications, 7th Ed., ©2014, Reprinted by permission of Pearson Education Inc., New York.
Problem 2
Q

A delivery truck travels 21 blocks north, 16 blocks east, and 26 blocks south. What is its final displacement from the origin? Assume the blocks are equal length.

A
17 blocks [73 E of S]17 \textrm{ blocks } [73^\circ \textrm{ E of S}]
Giancoli 7th Edition, Chapter 3, Problem 2 solution video poster
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VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. This delivery truck initially drives 21 blocks north and then 16 blocks east and 26 blocks south. So its displacement is given by this vector which connects the origin to the destination and it has a x-component this way which is equal to the 16 blocks and it has a y-component which is the 26 blocks south minus 21 blocks north for a total of 5 blocks south. So the magnitude of this resultant by using Pythagoras and we have the square root of the y-component of the resultant squared plus the x-component of the resultant squared. So that's square root of 5 squared plus 16 squared and that gives about 17 blocks. And then we'll take this angle in here; this is gonna be the angle to the east of south and that's the inverse tangent of the opposite which is 16 divided by the adjacent which is 5 and that gives about 73 degrees east of south and it's going 17 blocks.

COMMENTS
By joseotilio25 on Sat, 2/28/2015 - 3:19 AM

Hello why E of S is the same if I said S of E

By Mr. Dychko on Mon, 3/2/2015 - 11:00 PM

Hi joseotilio25, is your question "is saying E of S the same as saying S of E"? If so, then nope, those are not the same. Saying 7373^\circ East of South means 7373^\circ towards the East, starting from South, whereas S of E means starting at East and measuring 7373^\circ towards the South.

By Vortex on Sat, 10/26/2019 - 7:31 PM

Hello, I believe Tan should have been reverse (Opposite/Adjacent) so (5/16).

By danewiren on Thu, 11/28/2019 - 10:51 PM

He did do opp/adj. Look at the angle he is looking for in the video.
16/5 is correct.

By bcit_physics on Sat, 10/17/2020 - 11:44 PM

hello, would 17 degrees south of east be a right answer as well?

By Mr. Dychko on Thu, 12/3/2020 - 10:53 PM

Yes, definitely, 17 degrees South of East is co-terminal with 7373^\circ East of South.

By GnosisFreu on Mon, 1/16/2023 - 8:00 PM

Why do we flip the tangent-1 (y/x)? I'm confused as to why we don't use (5/16) and instead, (16/5) since 5 is supposed to be y and 16 is supposed to be x.

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