1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

A sailboat traveling east

  1. Jan 31, 2015 #1
    1. The problem statement, all variables and given/known data
    A sailboat is traveling due east, with a speed V=Vinit at time t = 0 and a constant eastward acceleration A(motor). From a time t = t(gust) to a time t=t(calm), a gust of wind gives the boat an additional acceleration A(wind) at an angle 60o North of East. Find an expression in terms of the quantities given for the North and East components of the boat's velocity at the time t(calm).

    2. Relevant equations
    Just basic 2 dimensional kinematic like
    Vfs= Vis + Ast
    Sf= Si+ Vis(t) + 1/2 As(t)^2

    3. The attempt at a solution



    I thought about this and think East components = Vinit + ( A motor + A wind (1/2)) (tcalm-t0)
    and North components = A wind (√3/2) (tcalm-t0)

    I mostly added the vectors of A wind and A motor, I am not sure if that is right. Please clarify or correct me if I am wrong, thank you.
     
  2. jcsd
  3. Jan 31, 2015 #2

    Nathanael

    User Avatar
    Homework Helper

    Why from t0 to t(calm)? Is that the correct time period in which the wind is blowing?

    Again, is that the time that the wind acts?
     
  4. Jan 31, 2015 #3
    I wasn't sure if from t0 to Tgust there was a time difference.
    If the point where Tgust happens then it would only be from Tcalm-Tgust.
    Is the rest of it correct?
     
  5. Feb 1, 2015 #4

    Nathanael

    User Avatar
    Homework Helper

    If they say it starts at tgust then you shouldn't assume tgust=t0

    The rest is correct, but write out the equation for the East component so I can see that you do it correctly.
     
  6. Feb 1, 2015 #5
    Well for the East component we have a Vinit and 2 acceleration component acting on it. Which are Amotor and Awind.
    And we know that Awind is 60 degree north east so the Awind in the east direction would be equal to Awindcos60degree

    So Velocity for the East component is equal to Vinit+ (Amotor + Awind cos 60) (tgust-tcalm).
    Does it look correct?
     
  7. Feb 1, 2015 #6

    Nathanael

    User Avatar
    Homework Helper

    Did we only turn on the motor on once the wind starting blowing?
     
  8. Feb 1, 2015 #7
    No... :(
    That was the part where I was confused and wasn't sure how to approach it.
    I know that from t0 to tgust the motor was running, but I wasn't sure how to incorporate it.

    V east= Vinit + (motor (t0-tgust))+ (motor + wind)(tcalm-tgust)...
     
  9. Feb 1, 2015 #8

    Nathanael

    User Avatar
    Homework Helper

    Write it in pieces. What is the velocity once the wind starts blowing? Then what is the velocity after the wind stops blowing?

    Also I just noticed one more small error. You wrote (tgust - tcalm), does anything seem wrong with that?
     
  10. Feb 1, 2015 #9
    Yeah it should be (tcalm - tgust) good catch.
    Well it goes from Vinit+ (motor(tgust-t0)) when the wind start.
    Then once it stop then wouldn't it be that plus ( motor + windcos 60)(tcalm-tgust).

    so it would be Vinit + (motor (tgust-t0))+ (motor +windcos 60)(t calm-tgust).
    Is that right?
     
  11. Feb 1, 2015 #10

    Nathanael

    User Avatar
    Homework Helper

    Yep :) (You can simplify it slightly because t0=0)
     
  12. Feb 1, 2015 #11
    Oh and an edit my to North Component it should be = A wind (√3/2) (tcalm-tgust)
    since no north component was acting it on from t0 until tgust.

    You are awesome, thank you for the help!
     
  13. Feb 1, 2015 #12

    Nathanael

    User Avatar
    Homework Helper

    Indeed

    You're welcome
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: A sailboat traveling east
  1. Vectors and sailboats? (Replies: 2)

  2. Sailboat problem (Replies: 1)

Loading...