# What is the Significance of Line of Action of Force?

• logearav
In summary, the first diagram shows F1 and F3 as projecting outward to the sides of the loop, while the second shows them as perpendicular to the B field.
logearav

## Homework Statement

http://www.xamidea.in/cbse-examination-guide.aspx?q=3&c=67&t=10000638&info=title

## Homework Equations

Dear members,
In this link, forces f2 and f4 are equal and opposite but they have same line of action
forces f1 and f3 are also equal and opposite but they have different line of action.
I don't understand how f1 and f3 have different line of action and f2 and f4 have same line of action, because both in both cases forces are equal and opposite

## The Attempt at a Solution

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The problem I think you have is because the first image is a little confusing since it doesn't give any feeling of 3d space. You must consider both figs and apply the LHR you can see that both F1 and F3 are parallel and both perpendicular to the B field but they are not doth on any single line perpendicular to the B field.They do not act on the same line except when the B field is perpendicular to the plane of the loop.

Sir, Thanks for the reply. I got it 80 % now, after re reading your reply. But one more doubt, that is, the second diagram shows F1 and F3 in upward and downward directions but in the first diagram, they are projecting outward to the sides of the loop. Why such a difference between the first and second diagram.

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"but they are not DOTH on any single line perpendicular to the B field.They do not act on the same line except when the B field is perpendicular to the plane of the loop."

I don't understand this line of your reply sir. What do u mean by DOTH?

logearav said:
Sir, Thanks for the reply. I got it 80 % now, after re reading your reply. But one more doubt, that is, the second diagram shows F1 and F3 in upward and downward directions but in the first diagram, they are projecting outward to the sides of the loop. Why such a difference between the first and second diagram.

There isn't any difference. The first diagram shows you the loop from the side of the loop ,you are looking towards the yz plane. The second shows you the loop at the same time from above ,you are looking at the xy plane. The problem is that the first diagram makes F1 and F3 look like they are not perpendicular to the B field. This is not what happens, the forces are always perpendicular to the B field and the current.It is just a bad diagram with no axes. .

logearav said:
What do u mean by DOTH.
Sorry it was a typo,I meant "BOTH".

Thanks a lot sir. What a beautiful explanation! I wonder why my physics teacher does not know all these things. Thanks again sir.

## 1. What is the definition of "line of action of force"?

The line of action of force is an imaginary line that represents the direction in which a force is acting on an object. It is always parallel to the direction of the force and extends infinitely in both directions.

## 2. How is the line of action of force determined?

The line of action of force is determined by the direction of the force and the point at which it is applied on the object. This point is known as the point of application. The line of action is a straight line passing through the point of application and extending in the direction of the force.

## 3. Does the line of action of force change if the point of application changes?

Yes, the line of action of force changes if the point of application changes. This is because the direction of the force and the point of application determine the line of action. If either of these factors change, the line of action will also change.

## 4. What is the significance of the line of action of force?

The line of action of force is significant because it helps us understand the effect of a force on an object. It allows us to determine the direction of movement or rotation of an object when a force is applied and also helps us calculate the magnitude of the force.

## 5. Can the line of action of force be at an angle to the direction of the force?

Yes, the line of action of force can be at an angle to the direction of the force. However, the line of action will always be parallel to the direction of the force and will not change unless the direction or point of application changes.

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