# Statics Problem - understanding the directions.

• kpx001
In summary, the person is confused about when to make the force negative in a problem and is seeking clarification. The expert explains that the direction of the force does not matter, but rather the direction of the torque, which can be either clockwise or anti-clockwise. They also point out an error in the person's calculation and provide the correct answer.
kpx001

## Homework Statement

Ok so basiclly I know how to do the problems, but I'm confused when to make the force negative and when to ignore the negative.

forexample: http://yfrog.com/jastaticsprobp
solving part a:
Moment at A = -24*39 -(-14*39) = 2028
notice how i had to do -(-14*39) to compensate for the force going down

VS.

http://yfrog.com/jqstaticsprob2p

where solving for
Moment at xaxis= -230*.250- 230*.210 = -105.8
notice i did not do -(-230*.210)

My assumption?
either keep the direction of force if the problem is 2-D ?? i have no idea, can someone help make this clear? thanks

Hi kpx001!

"up" and "down" doesn't matter, what matters is "clockwise" and "anti-clockwise" …

so in both your pictures, the torque (the moment) is clockwise for both forces, so they have the same sign (and your answer to the first is wrong).

In statics problems, it is important to consider the direction of the forces and their corresponding moments. When calculating moments, the direction of the force should be taken into account. In the first example, the force at point A is pointing downwards, so it should be represented as a negative value in the calculation. However, in the second example, the force is acting in the same direction as the axis, so it does not need to be represented as a negative value. It is important to carefully consider the direction of the forces and their effects on the calculation of moments in order to accurately solve the problem. This will ensure that the final answer is correct and reflects the actual physical situation.

## 1. What is the difference between scalar and vector quantities?

Scalar quantities are physical quantities that have only magnitude, such as mass or temperature. Vector quantities have both magnitude and direction, such as force or velocity.

## 2. How do I determine the direction of a vector?

The direction of a vector can be determined by using a compass or protractor, or by using the right-hand rule. The right-hand rule states that if you curl your right hand fingers in the direction of the vector, your thumb will point in the direction of the vector.

## 3. Can the direction of a vector be negative?

Yes, the direction of a vector can be negative. This means that the vector is pointing in the opposite direction of the positive direction.

## 4. How do I add or subtract vectors with different directions?

To add or subtract vectors with different directions, you must first resolve them into their horizontal and vertical components. Then, you can add or subtract the components separately to get the resultant vector.

## 5. What is the difference between displacement and distance?

Displacement is a vector quantity that measures the shortest distance between two points in a specific direction. Distance is a scalar quantity that measures the total length of the path traveled, regardless of direction.

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