Vector Addition Problem - Statics

In summary: That's a relief ! In summary, the conversation discusses finding the magnitude and direction of the resultant force by using basic vector addition, the law of cosines, and the law of sines. The attempt at a solution involves finding an intermediate vector, F', and then adding it to the third vector, F3, to get the final resultant force, Fr. An alternative method is also mentioned, which involves calculating the x and y components of each vector and then adding them to get the final components. The final x and y components are found to be +9.7 N in the x-direction and +28 N in the y-direction, resulting in a magnitude of 29.6 N and an angle of 19 degrees from the
  • #1
Jack_M
6
0

Homework Statement


Find the magnitude and direction of the resultant force Fr=F1+F2+F3 by first finding F'=F1+F2 then Fr=F'+F3

known values are in the link

Homework Equations


Basic vector addition. Law of cosines. Law of sines.

The Attempt at a Solution


Here's my attempt. I'm not convinced by my answer.
http://imgur.com/LcrFApu
 
Last edited by a moderator:
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  • #2
Jack_M said:

Homework Statement


Find the magnitude and direction of the resultant force Fr=F1+F2+F3 by first finding F'=F1+F2 then Fr=F'+F3

known values are in the link

Homework Equations


Basic vector addition. Law of cosines. Law of sines.

The Attempt at a Solution


Here's my attempt. I'm not convinced by my answer.
http://imgur.com/LcrFApu

Another way of calculating the force is using x and y components. Add up all of the x components and all of the y-components of the three vectors to get the x and y components of the final vector. This saves you the trouble of calculating an intermediate vector.

x component = magnitude * cos (theta) -- theta measured from +x axis; y-component = magnitude * sin (theta) -- again theta measured from +x axis.
 
Last edited by a moderator:
  • #3
Hello Jack, welcome to PF :)

F' is just fine.
Fr magnitude is fine too. Check the angle calculation. From your drawing you can already see that 29.12 degrees looks to be too low.

Of course, Quantum D gives a good alternative -- that should be equivalent, but I don't know if that's what the exercise wants you to do.
 
  • #4
BvU said:
Hello Jack, welcome to PF :)

F' is just fine.
Fr magnitude is fine too. Check the angle calculation. From your drawing you can already see that 29.12 degrees looks to be too low.

Of course, Quantum D gives a good alternative -- that should be equivalent, but I don't know if that's what the exercise wants you to do.

I get essentially the same numbers that are in the box using x, y vectors: 19 degrees, 29.6 N
 
  • #5
QD, I would've much rather have done it using component method, however my professor would take off points.

BvU, are you referring to the 29.67N as being the correct magnitude for Fr and 19.12 degrees being incorrect? Could it be 19.12 degrees from the vertical?
 
  • #6
Quantum Defect said:
I get essentially the same numbers that are in the box using x, y vectors: 19 degrees, 29.6 N
That's reassuring. Thanks for checking!
 
  • #7
Jack_M said:
That's reassuring. Thanks for checking!
My final x components were: +9.7 N x^ direction, +28 N y^ direction -- using inverse tangent gives me 19 degrees from y-axis, as you conclude above.
 
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  • #8
To reassure you both: I've been brainwashed to zero degrees ##\equiv## positive x-axis direction. So I find 1.237 (radians, that is. The one and only reasonable unit for angles :) -- did I also say the brainwashing included ##2\pi## for a full circle ?) And I really am a physicist !

So we all agree and Jack can shed his uncertainty on this subject.
 

1. What is a vector addition problem in statics?

A vector addition problem in statics is a mathematical problem that involves adding two or more vectors together. Vectors are quantities that have both magnitude (size) and direction, and they are commonly used to represent forces, velocities, and displacements in physics and engineering.

2. How do I solve a vector addition problem in statics?

To solve a vector addition problem in statics, you first need to identify all the given vectors and their magnitudes and directions. Then, use the graphical or analytical method to add the vectors together. The graphical method involves drawing the vectors to scale on a graph and using the parallelogram or triangle rule to find the resultant vector. The analytical method uses trigonometry and the Pythagorean theorem to find the magnitude and direction of the resultant vector.

3. What is the difference between scalar and vector addition in statics?

Scalar addition and vector addition are two different operations in statics. Scalar addition involves adding quantities that have only magnitude, such as mass or temperature. On the other hand, vector addition involves adding quantities that have both magnitude and direction, such as force or velocity. Scalar addition follows the regular rules of arithmetic, while vector addition follows specific graphical or analytical methods.

4. Can I use the same method to solve all vector addition problems in statics?

No, there are different methods for solving vector addition problems in statics depending on the given information. If the vectors are given in component form, you can use the rectangular or Cartesian method. If the vectors are given in magnitude and direction form, you can use the polar or trigonometric method. It is important to understand and choose the appropriate method for each problem.

5. Why is vector addition important in statics?

Vector addition is important in statics because it allows us to accurately represent and analyze physical quantities such as forces, velocities, and displacements. It also helps us to understand the overall effect of multiple forces acting on an object, which is crucial in engineering and physics applications. Additionally, vector addition is a fundamental concept in higher-level mathematics and physics courses.

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