SAT physics question -- Flag on a bicycle being ridden in the wind...

  • Thread starter YMMMA
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  • #1
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Homework Statement


A girl is riding a bicycle at 15 miles per hour due north. A steady wind is blowing at 15 miles per hour from the east. A flag mounted on the bicycle will be stretched out toward the
(A) west (B) south (C) southwest (D) southeast (E) northeast

Homework Equations


Vector addition

The Attempt at a Solution


I drew an arrow pointing north then from its head i drew an arrow pointing east
I got E for the resultant vector. Is that right?
 

Answers and Replies

  • #2
berkeman
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Homework Statement


A girl is riding a bicycle at 15 miles per hour due north. A steady wind is blowing at 15 miles per hour from the east. A flag mounted on the bicycle will be stretched out toward the
(A) west (B) south (C) southwest (D) southeast (E) northeast

Homework Equations


Vector addition

The Attempt at a Solution


I drew an arrow pointing north then from its head i drew an arrow pointing east
I got E for the resultant vector. Is that right?
Welcome to the PF. :smile:

If the wind is "blowing from the east", the vector that represents it will not be pointing toward the east. Which way would it point?

Also, you should probably draw a free body diagram (FBD) of the flag to help you reason this problem out. Do you know how to do that? Show the forces of the two wind components on the flag...
 
  • #3
156
10
Ahhhh, It says ‘from the east’ that means its directed west. Ugh, I should read well next time.
Thats how i draw the FBD. So, the answer is C.
 

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  • #4
berkeman
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The correct answer is indeed C, but your vectors are still not quite right. You want the vectors to represent the wind forces on the flag. When the bike rider rides north, which was is the apparent wind blowing on the flag? :smile:
 
  • #5
156
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Oh, its west of south..
Do you mean the vector of the wind is from the tail of the north vector and directed west?
 
  • #6
berkeman
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Oh, its west of south..
What's west of south?
Do you mean the vector of the wind is from the tail of the north vector and directed west?
I'm not sure what that means, sorry.

You have drawn the horizontal wind force vector correctly. Since the wind is coming from the east, the wind force from it is toward the west.

Since the bicycle is moving toward the north, the apparent wind force on the flag from that motion is pointing toward the ________
 
  • #7
156
10
Sorry, I mean south of west.
I understood it. Now, I can imagine it pointing toward the south as a result of the motion.
Thanks a lot!!
 
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