Finding Parallel/Perpendicular Forces & Normal Force

In summary, the person is asking for help with finding the parallel, perpendicular, and normal forces. They are given a weight, angle, and tension, and are supposed to use these to solve for the net forces. The box is not accelerating, so the net force is zero. The person is then asked to break the net force equation into its X and Y components. They are then asked to find the values for Fg(x) and Fg(y), which are calculated using the values for Ft and Fn.
  • #1
jubbly
22
0
Hey guys, I was wondering if you can help tell me if I am doing this right for finding the parallel and perpendicular force.

To find the parallel force would I have to take: gravity*sin(theta) or would I have to take the weight? Same goes with the perpendicular force, but using cosine.

Also to find the normal force would I take the weight-tension*sin(theta)?

Thanks for your help.
 
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  • #2
Force of what? Do you have a specific situation? It's not so much parallel and perpendicular. What you're finding there are the components of that force in the x, and y axes.

Now your normal force for example is applied by a surface in response to the force applied by an object resting on it. Remember, for every action there is an equal and opposite reaction. If you have a box sitting on a table, gravity pulls down on the box. This exerts a downward force on the table, which in turn exerts a force of equal magnitude back in the opposite direction. If you were pushing down on said box, the normal force would then be equal to the force of gravity, plus the force you were applying to the box.
 
  • #3
I'm just analyzing forces with numbers given to me.
The weight, tension, and the angle is the only given I have.
 
  • #4
Well posting the actual question would be helpful.
 
  • #5
It's just a table, titled analysis of forces.
I am supposed to use the weight, angle, and tension given to find the perpendicular, parallel and normal forces.

The weight I have is -10 at an angle of 15 degrees and the tension is 1.5.
Sorry if I can't be anymore clearer than this, not very good at physics.
 
  • #6
I see then. Okay. You can solve pretty much any physics problem with three steps:

1. Free body diagram
2. Net force equation
3. Solve it

Do you know what a free body diagram is, and how to properly make one?
 
  • #7
I don't know about properly making one, but I do know what it is.

So if I drew one at an angel of 0 it would look like a straight line with an object in the middle?
Then I would draw a arrow below the object labeling that Fg and on top of the object would be FN. Is there anything else I am missing?
 
  • #8
Well you're supposed to draw them originating from the centre of the object. You have the correct idea I think. Fg points down, Fn points up, and Ft points in whatever direction Ft points in. Your 0 angle should be parallel with the positive X axis (pointing to the right).

Looking at that description I'd have to say the object is on a 10 degree incline with a rope pulling up the slope.

Now that you have your forces figured out, it's time to put them into a net force equation.

Now your box isn't accelerating, so using Fnet=ma your net force is equal to zero. Therefore Fnet=Ft+Fg+Fn=0.

Now you need to break it up into your X and Y components. Let's rotate our reference frame to make the incline zero degrees. So now your Fg is acting at a 15 degree angle relative to your reference frame.

Looking at the components now, you have in your X axis:
Fnet=Fg(x)+Ft=0
and in your Y axis
Fnet=Fg(y)+Fn=0

Now you can rewrite these as:
Fg(x)=Ft
Fg(y)=Fn
Do you see why you can do this?
 
  • #9
Oh, now I understand. Thanks for clearing things up for me!
 

1. What is the difference between parallel and perpendicular forces?

Parallel forces act in the same direction, while perpendicular forces act at right angles to each other.

2. How do you calculate the normal force in a given situation?

The normal force is equal to the force of gravity on an object in a given situation. It can be calculated using the equation FN = mg, where m is the mass of the object and g is the acceleration due to gravity.

3. Can parallel and perpendicular forces cancel each other out?

Yes, if the forces are equal in magnitude and opposite in direction, they can cancel each other out resulting in a net force of zero.

4. What is the purpose of finding parallel and perpendicular forces?

Understanding parallel and perpendicular forces is important in many fields such as engineering, physics, and architecture. It allows us to analyze and predict the effects of forces on structures and systems.

5. How can you determine the direction of the normal force?

The normal force always acts perpendicular to the surface an object is in contact with. It points away from the surface and is always perpendicular to the force of gravity.

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