Vectors with forces and trig help.

Dhob28

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Feb 8, 2019
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Hi,

Can anyone assist with the below problem? I am not necessarily looking for the answer, more guidance on how to find the answer. Thanks in advance.

Vector question 2TMA03.jpg

Question is:

The magnitude of the forces A and B acting on the platform are:|A| = 725.0 kN
|B| = 615.0 kN
If the system is stationary, what is the magnitude of force C?
Show all your working clearly and give your answer in kN to 3 significant figures



 
View attachment 11002

Question is:

The magnitude of the forces A and B acting on the platform are:|A| = 725.0 kN
|B| = 615.0 kN
If the system is stationary, what is the magnitude of force C?
Show all your working clearly and give your answer in kN to 3 significant figures

There are several ways you can approach this sort of problem, and several notations that are common. For that reason, it would be very helpful if you could show some work, so we could try to use the methods and notation you are learning.

One approach is to find the resultant of A and B, and observe that C must be the opposite (so that there is no net force).

Another is to define the components of C as variables and write one equation saying that the sum of the horizontal components is zero, and another for the vertical components. (Or rather, east-west and north-south.)

Then use the components you get for C to find its magnitude.
 
There are several ways you can approach this sort of problem, and several notations that are common. For that reason, it would be very helpful if you could show some work, so we could try to use the methods and notation you are learning.

One approach is to find the resultant of A and B, and observe that C must be the opposite (so that there is no net force).

Another is to define the components of C as variables and write one equation saying that the sum of the horizontal components is zero, and another for the vertical components. (Or rather, east-west and north-south.)

Then use the components you get for C to find its magnitude.

Many thanks for the response Dr. Peterson. The next question relates to the resultant force so I am assuming the correct method would be to find the resultant of A and B? I have pasted below the full question.

Tug A is heading west and tug B is heading south. The figure above shows the approximate direction of tug C.
  • a.If the system shown is not moving (i.e. it is static), describe how the forces operating on the platform relate to one another.
    Write this relationship mathematically using vector notation.
    Draw a vector diagram showing how these forces can be added together and how the heads and tails of each vector relate to each other (see the Part 2 book, Figure 13.25 (p. 197) for an example of a vector diagram).
    (3 marks)
  • b.The magnitude of the forces A and B acting on the platform are:
    |A| = 725.0 kN
    |B| = 615.0 kN
    If the system is stationary, what is the magnitude of force C?
    Show all your working clearly and give your answer in kN to 3 significant figures.
    (4 marks)
  • c.The drilling platform has to be moved directly west. In order to achieve this, what would have to happen to the resultant force acting on the platform?
    Suggest two ways the individual forces could be changed to achieve this resultant force. You may change the magnitude and direction of any of the individual forces to achieve this.
    (3 marks)
total: 10 marks
 
You haven't shown work, which is what I primarily asked for, in order to see what style of work you are being taught (components, or trigonometry, or whatever), and where you are stuck.

But part of the answer to (a) will be A + B + C = 0, and the answer to (b) will be calculated, one way or another, as C = -(A + B), so, yes, the resultant will be involved in some way, but it isn't directly asking for that.
Note that (c) is open-ended, with several possible answers.
 
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