What is your friends speed relative to you?

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SUMMARY

The discussion focuses on calculating the relative speed between two individuals crossing a river with a current. The river is 100 meters wide, with a current of 8.5 m/s at a 45-degree angle southeast. One individual travels at 7 m/s directly north, while the other travels at 7 m/s directly south. The calculated relative speed of the friend to the individual is 14 m/s, and it takes 100 seconds to cross the river, factoring in the current's effect on their movement.

PREREQUISITES
  • Understanding of vector addition in physics
  • Knowledge of relative velocity concepts
  • Familiarity with trigonometric functions for angle calculations
  • Basic principles of motion in fluid dynamics
NEXT STEPS
  • Study vector addition in physics to enhance understanding of relative motion
  • Learn about the effects of currents on boat navigation
  • Explore trigonometric applications in real-world scenarios
  • Investigate fluid dynamics principles relevant to moving objects in water
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Students studying physics, particularly in mechanics and fluid dynamics, as well as educators looking for practical examples of relative motion and vector analysis.

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Homework Statement




There's a 100m wide river, with a current of 8.5 m/s going 45 degrees SE. You and a friend are standing directly opposite each other across the river, the friend on the north side, you on the south side. You each get in boats that travel 7 m/s relative to the water and head out directly north/south.

a. What is your friends speed relative to you?

...
d. How long does it take to cross the river?

Homework Equations





The Attempt at a Solution



Just looked over briefly at some of them, can someone verify if these look correct?

A is 14 m/s

D Since you will be traveling 1 m/s north (the current vector will push 6 m/s down on you), it will take 100 s to cross it.
 
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looks fine to me
 

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