i hope this makes sense.
Say that i have x and y axis. then i have an arrow coming out similiar to how you would draw a resultant arrow in physics.
the arrow represents Force=140N
Then say that you have to find the moment about O and the origin is O.
So the first step is to find Fx and Fy.
Then you use M=Fd to solve the problem but you also have to use the right hand rule to figure out the direction for each force and distance.
Say that Fx=4i. I know to find the direction you do rXF. But when i use the right hand rule, after i put my hand in the r direction, do i curl my finger in the F direction or the Fx direction.
also i have solutions to my textbook. Sometimes they say that clockwise is positive and counterclockwise is positive. How do you decide whether each is positive or not. I thought usually, counterclockwise was positive
counterclockwise is positive.
http://en.wikipedia.org/wiki/Right_hand_rule
you didn't answer my other question about which force to use.
To clarify, you have an arrow representing a force of 140N on an x-y axis, and you want to find the moment about point O.
To find the components Fx and Fy, you can use trigonometry. Let's assume that the angle between the x-axis and the arrow representing the force is θ.
1. The x-component, Fx, can be found using the formula Fx = F * cosθ.
2. The y-component, Fy, can be found using the formula Fy = F * sinθ.
Regarding the right-hand rule for finding the direction of the moment, you need to curl your fingers in the direction of the force (Fx in this case) and then point your thumb in the direction of r (the distance vector to point O from the line of action of the force). This will give you the direction of the moment.
When it comes to determining whether the clockwise or counterclockwise direction is positive, it may vary depending on the convention used in your textbook or problem. In some cases, counterclockwise may be considered positive, while in others, clockwise may be considered positive. It's best to refer to the specific context or instructions provided to determine the correct sign convention for the moment in your problem.
If no specific convention is given, it is common to consider counterclockwise (or anti-clockwise) direction as positive. However, it's important to confirm this by referring to the guidelines or instructions given in your textbook or by your instructor. Following the specified convention ensures consistency and accuracy in solving problems.