Basic question about coplanar forces

  • Thread starter Elevenses
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In summary, the question is about finding the resultant of five coplanar forces, but the focus is on understanding the discrepancy between the magnitude and x-component of the second force, which is 15.0N and 7.5N respectively. This is because the x-component of a force is calculated using the cosine function, resulting in a value that is half of the original magnitude. With this clarification, the confusion is resolved and the first two forces can be properly analyzed.
  • #1
Elevenses
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Summary:: Adult brand new to maths and physics and starting from the bottom, just for a hobby. I'm working my way through Schaum's Outline of College Physics and cannot understand why the N unit in the below table goes from 15.0N to 7.5N. Total beginner here, and help appreciated :)

I have written this out rather than copy-and-pasted from the textbook in case of copyright reasons. The question is to find the resultant of these five coplanar forces. I have just given the first two forces here because I cannot understand where the 7.50N is coming from although this issue is repeated for the following forces.

Force - - - - x-Component - - - - - - - - - - - - - - - - - - - y-Component

19.0N - - - - 19.0N - - - - - - - - - - - - - - - - - - - - - - - - - 0N
15.0N - - - - (15.0N) cos 60.0 degrees = 7.50N - - - - (15.0N) sin 60.0 degrees = 13.0N

I start off from origin and go along x-axis with the first force, 19.0N. So far so good. Then I move around 60.0 degrees and draw in the second force, 15.0N, only then this becomes 7.50N. Not getting that when Rx = ΣFx, the 15.0N is 7.50N? Thanks!
 
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  • #2
Elevenses said:
the second force, 15.0N, only then this becomes 7.50N.
15N is the magnitude, 7.5N is the x-component
 
  • #3
A.T. said:
15N is the magnitude, 7.5N is the x-component

Thanks for this. Like with so many things, the second it's pointed out it seems so obvious. Now it makes sense why the first Force and x-Component were both 19.0N. 👍:smile:
 

Related to Basic question about coplanar forces

1. What are coplanar forces?

Coplanar forces are forces that act on the same plane or in the same direction. This means that they have the same line of action and lie on the same geometric plane.

2. How do coplanar forces affect an object?

Coplanar forces can either cause an object to remain at rest or to move in a specific direction. They can also change the direction or magnitude of an object's motion.

3. What is the difference between concurrent and non-concurrent coplanar forces?

Concurrent coplanar forces have a common point of intersection, while non-concurrent coplanar forces do not. Concurrent forces are easier to analyze because they can be reduced to a single resultant force, while non-concurrent forces require vector addition to determine the resultant force.

4. How do you calculate the resultant force of coplanar forces?

The resultant force of coplanar forces can be calculated by using vector addition. This involves finding the sum of the individual forces by adding their magnitudes and taking into account their direction. The resultant force is the single force that has the same effect as all the individual forces combined.

5. Can coplanar forces cancel each other out?

Yes, coplanar forces can cancel each other out if they are equal in magnitude and opposite in direction. This is known as equilibrium and it means that the object will remain at rest or continue to move at a constant velocity.

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