Solving for F_T, F_N, and alpha

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In summary, the conversation is about a person seeking help with a physics problem involving a stepladder. They typed out their attempt at a solution and discovered a mistake, leading to the correct answer. The conversation also includes equations and a template for solving the problem.
  • #1
Haru Yo Koi
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Thank you!

A very frustrating problem involving physics, and I finally decided to create an account and ask. And I typed up my problem, equations and all. But as I typed a certain equation, I suddenly wondered why I had cos in one place and sin in another. That was a mistake, and after fixing it, the answer turned up correct!

(Because I don't feel like losing my hard-typed stuff, it is saved below, or at least the beginning of it. There didn't seem a point in adding to it.)

Homework Statement



GIANCOLI.ch12.p28.jpg


A 60.0-kg person stands 2.0 m from the bottom of the stepladder shown in the figure above. The horizontal rod is halfway up the ladder.

Find the tension in the horizontal rod, the normal forces on each side of the ladder, and the angle/direction of the force one side of the ladder exerts on the other.

Homework Equations



Sum of torque = 0. Sum of forces in each direction = 0.

The Attempt at a Solution



I'm trying to look at each side of the ladder separately.

The left seems to have four forces: A normal force [tex]F_{N}[/tex] which points straight up, a tension force [tex]F_{T}[/tex] which points straight rightwards, a [tex]F_{p}[/tex] which points straight downwards, and a [tex]F_{0}[/tex] which points upwards to the left at an angle [tex]\alpha[/tex] from the horizontal.

The right side seems to be the same, except that [tex/]F_{0}[tex] points downwards [tex]\alpha[/tex] from the horizontal and the normal force [tex]is F_{n}[/tex].

Now some equations can be found.
[tex]F_{0}sin(\alpha)=F_{n}
F_{0}cos(\alpha)=F_{T}
F_{N} + F_{0}sin(\alpha) = F_{p}
(1/2)F_{t}sin(\theta) = F_{n}cos(\theta)
(1/5)F_{p}cos(\theta)+(1/2)[/tex]

At this point I realized that what was on the right, which I had down as F_N(cos theta) should actually have been F_N(sin theta).
 
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  • #2


This template wasn't designed for nothing. It really helps.
 

FAQ: Solving for F_T, F_N, and alpha

What is the purpose of solving for F_T, F_N, and alpha?

Solving for F_T (total force), F_N (normal force), and alpha (friction angle) is important for understanding and predicting the behavior of objects on inclined planes and surfaces. It allows us to determine the forces acting on the object and how they affect its motion.

How do I calculate F_T, F_N, and alpha?

To calculate F_T, we use the equation F_T = mgsin(theta), where m is the mass of the object, g is the acceleration due to gravity, and theta is the angle of inclination. F_N can be calculated by using the equation F_N = mgcos(theta). The value of alpha is determined by using the equation tan(alpha) = F_F/F_N, where F_F is the friction force.

What factors affect the values of F_T, F_N, and alpha?

The values of F_T, F_N, and alpha are affected by the mass of the object, the angle of inclination, and the coefficient of friction between the object and the surface it is on. Additionally, external forces such as air resistance or applied forces can also affect these values.

How does the value of alpha affect the motion of an object?

The value of alpha, or the friction angle, determines the maximum angle at which an object can remain at rest on an inclined surface without sliding. If the angle of inclination is greater than the friction angle, the object will begin to slide down the surface. Therefore, a higher friction angle means the object can remain at rest at steeper angles.

Can I use these equations for any inclined surface?

These equations can be used for any inclined surface, as long as the surface is not accelerating. If the surface is accelerating, additional equations for calculating the net force and acceleration of the object must be used in conjunction with the equations for F_T, F_N, and alpha.

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