Question involving velocities and distance

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Homework Help Overview

The problem involves two soccer players, Mary and Jane, running in different directions with specified velocities. The questions focus on their relative positions and velocities over time, specifically how long it takes for them to be a certain distance apart, the relative velocity of one player to the other, and their separation after a given time.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants discuss the need to convert velocity vectors into distances and explore the relationship between time and distance. There is an attempt to use vector addition for relative velocities, and questions arise about the correctness of this approach.

Discussion Status

Some participants have provided hints and guidance, suggesting that addressing the relative velocity first may simplify the problem. There is an ongoing exploration of vector addition versus subtraction for calculating relative velocities, with no clear consensus reached yet.

Contextual Notes

The original poster mentions a time constraint due to an upcoming test, indicating a sense of urgency in resolving the problem. There is also a reference to specific angles and directions that may complicate the calculations.

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Homework Statement


Two soccer players, Mary and Jane, begin running from nearly the same point. Mary runs in an easterly direction at 4 m/s, while Jane takes off in a direction 60 degrees north of east at 5.4 m/s. (a) How long before they are 25 m apart? (b) What is the velocity of Jane relative to Mary? (c) How far apart are they after 4 s?


Homework Equations


D=v/t
Yf=Yi+(Vy)iT+1/2at^2
Xf=Xi+(Vx)iT


The Attempt at a Solution


T must be the same value in both equations, but I do not know how to convert velocity vectors with a 60 degree separation into distance to solve the problem. I have a test tomorrow and your input would be much appreciated!
 
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Welcome to PF!

Hi drummerdimitr! Welcome to PF! :smile:

(try using the X2 tag just above the Reply box :wink:)

Hint: If you can answer (b) first, then (a) should be easy. :wink:
 
Thanks for the quick reply, I found the answer to part c by multiplying the velocities by 4 and finding the length of the third side. I tried doing vector addition and ended up with a relative velocity of 8.17 m/s at 34.9 degrees north degrees, but unfortunately, it is not the right answer. What am i doing wrong here?
 
(just got up :zzz: …)
drummerdimitr said:
I tried doing vector addition and ended up with a relative velocity of 8.17 m/s …

ahh … for relative velocities, try vector subtraction! :wink:
 

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