Finding the contact force in a hinge?

In summary, the question is about finding the contact force in the hinge of a system consisting of a 4m long beam attached to a wall with a wire and a hinge, with a 20kg sign attached to the beam. The system is in equilibrium at 20° to the horizontal. The equations used to find the tension in the wire and the force in the hinge are provided, and the final values for the tension and force are found to be 293.02 N and 291.9 N, respectively. The question also asks if the system is in equilibrium at any other point and what it means for a system to be in equilibrium.
  • #1
SopwithCamel
2
0
I have been working on a slightly tricky calculus problem and was hoping someone could verify my solution.

Homework Statement



A 4m long beam whose mass is 5 kg is attached to the wall by a wire and a hinge that allows the beam to rotate. There is a sign (with a mass of 20 kg) attached to the beam. The system is in equilibrium when the beam is at 20° to the horizontal. What is the contact force in the hinge (magnitude and direction)?

Homework Equations



The Attempt at a Solution



I first found the tension in the wire by setting the net torque to zero:
0=|r||T|sinθ + |rs||Fs|sinθ - |rb||Fb|sinθ
(where Fs is the force of the sign and Fb is the force of the beam and rs and rb is the distance of the forces from the hinge, respectively)
0=(4)(T)sin135 - (4)(196)sin110 - (2)(49)sin110
Solving for T, I get the tension in the wire = 293.02 N.

Then, to find the force in the hinge, I found two equations by resolving it into it's vertical and horizontal forces:
Horizontal: Tcos25 = Fcosθ ---> Fcosθ = 265.574N
Vertical: 0 = Fsinθ + Tsin25 - 49 - 196 ---> 245 = Fsinθ + 123.574N ---> Fsinθ = 121.161N

From there, I was able to solve... θ = 24.5° and F = 291.9N.


Is this correct? I hope this isn't asking too much... Please tell me if there are any errors in my figuring.

ALSO ... A quick question: When it says the beam is in equilibrium at 20° to the horizontal, does that imply that it is not at equilibrium at any other point? What exactly does it mean in this scenario to be "in equilibrium"?

Thank you!
 
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  • #2
This isn't a calculus problem. I've moved the thread to the intro physics forum.
 

Related to Finding the contact force in a hinge?

1. What is a contact force in a hinge?

A contact force in a hinge is the force that acts between two objects in contact with each other. In the case of a hinge, it is the force that is exerted between the two parts of the hinge, allowing it to rotate and maintain its position.

2. How do you calculate the contact force in a hinge?

The contact force in a hinge can be calculated using the equation F = kθ, where F is the contact force, k is the hinge's stiffness, and θ is the angle of rotation. The value of k can be determined experimentally or through mathematical modeling.

3. What factors can affect the contact force in a hinge?

The contact force in a hinge can be affected by various factors, including the stiffness of the hinge, the angle of rotation, the weight of the objects attached to the hinge, and any external forces acting on the hinge.

4. How does the contact force in a hinge change with different angles of rotation?

The contact force in a hinge is directly proportional to the angle of rotation. This means that as the angle of rotation increases, the contact force also increases, and as the angle decreases, the contact force decreases.

5. Why is it important to find the contact force in a hinge?

Finding the contact force in a hinge is important in understanding the structural integrity and stability of the hinge. It can also help in determining the appropriate hinge design and materials to use for a given application. Additionally, knowing the contact force can aid in predicting any potential wear or damage to the hinge over time.

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