A boat being pulled by two other boats with cables

  • #1
Lay1
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Homework Statement:
A ship is pulled at a constant speed by two small boats, A and B, as shown in Figure 4.27. The engine of the
ship does not produce any force. The tension in each cable between A and B and the ship is 4000 N.
a. Draw a free-body diagram showing the three horizontal forces acting on the ship.
b. Draw a vector diagram to scale showing these three forces and use your diagram to find the value
of the drag force on the ship
Relevant Equations:
Fx = Fcos n
Fy = Fsin n
FAx = F cos 40
FAy = F sin 40
2FAx = Drag
Drag = 6128N
The answer says 6200N
 

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Answers and Replies

  • #2
PeroK
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Your solution looks like one of those things you get during an eye test when the letters get smaller and smaller until you can't read them!
 
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  • #3
PeroK
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My spreadsheet says ##2*4000\cos(40) = 6128##.
 
  • #4
MatinSAR
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Drag = 6128N
The answer says 6200N
I think it should be 2(4000)cos40=6128.35N (40 degree)
It is better to share a picture from the answer which suggests it's 6200N.
 
  • #5
Orodruin
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The answer to me looks like one of those cases where the answer has rounded the intermediate result from 3064 N to 3100 N and then multiplied the rounded result by two, resulting in an erroneous rounding to 6200 N instead of 6100 N for the final result.
(Also note that 6128 N is too many significant digits given the precision of the input.)
 
  • #6
Orodruin
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Your solution looks like one of those things you get during an eye test when the letters get smaller and smaller until you can't read them!
This is what happens when one only cancels one out of two subscript tags ... 😏
 
  • #7
Steve4Physics
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Homework Statement
a. Draw a free-body diagram showing the three horizontal forces acting on the ship.
b. Draw a vector diagram to scale showing these three forces and use your diagram to find the value of the drag force on the ship
a) You haven't shown your answer to part a).

b) From the question's wording, it looks like you are expected to solve the problem using a scale diagram (not by using trig'). You need a pencil, paper, ruler and protractor. Don't forget to label the diagram appropriately, write the scale you are using, and give your working.
 
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  • #8
hutchphd
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The diagram shown by the OP is quite inaccurate. The angles look like <30 degrees. This will lead to confusion
 
  • #9
haruspex
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The diagram shown by the OP is quite inaccurate. The angles look like <30 degrees. This will lead to confusion
Since the student is asked to draw an accurate diagram, the book diagram will be deliberately a little inaccurate.
 
  • #10
Lay1
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Your solution looks like one of those things you get during an eye test when the letters get smaller and smaller until you can't read them!
I don't know why it turns out like that also.
 
  • #11
Lay1
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This is what happens when one only cancels one out of two subscript tags ... 😏
My spreadsheet says ##2*4000\cos(40) = 6128##.
Thanks. Next time I will be careful about the words.
 

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