Statics - mass attached to a string. Find forces acting to keep in equilibrium

In summary, the conversation is about a physics problem involving a light inextensible string of length 40cm and a mass of 2kg. The question asks for the magnitude of the horizontal force and the tension in the string. The solution involves using trigonometry to find the angle between the horizontal and the tension in the string, and then equating the vertical and horizontal components of the tension to the weight and horizontal force, respectively. The resulting values for the tension and force are T=22.6N and F=11.3N.
  • #1
HM10
2
0
Hey guys, this is my first time posting and I really need your help.

I'm stuck on this question:
A light inextensible string of length 40cm has its upper end fixed at a point A, and carries a mass of 2kg at its lower end. A horizontal force applied to the mass keeps it in equilibrium, 20cm from the vertical through A. Find the magnitude of this horizontal force and the tension in the string.

From this I think I only know one force which would be 2g. I also know the lengths but what to do with them?!
I'm guessing I have to use trigonometry? I'm really clueless and don't know where to start. I can't even think of what the diagram would look like. I'd appreciate any help!

I tried making a triangle, with sides 0.2,0.4 and 2g. Don't know how this will help tho :(

Thanks in advance
 
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  • #2
Hi HM, welcome to PF.
40 cm, 20 cm and vertical forms a right angled triangle. From that you can find the angle between the horizontal and the tension in the string. Then find the component of T in the vertical and horizontal direction. Equate the vertical component to mg and the horizontal component to force. And solve for F and T.
 
  • #3
rl.bhat said:
Hi HM, welcome to PF.
40 cm, 20 cm and vertical forms a right angled triangle. From that you can find the angle between the horizontal and the tension in the string. Then find the component of T in the vertical and horizontal direction. Equate the vertical component to mg and the horizontal component to force. And solve for F and T.

Thanks a lot for the help.I followed your instructions and got T=22.6N and F=11.3N which are the answers in the back!

Cheers :)
 

1. What is statics in physics?

Statics is a branch of physics that deals with the study of objects at rest or in a state of constant motion. It involves analyzing the forces acting on an object and how they interact to keep the object in equilibrium.

2. What is the purpose of finding the forces acting on an object in equilibrium?

The purpose of finding the forces acting on an object in equilibrium is to understand the balance of forces that keep the object in a state of rest or constant motion. This allows us to predict and control the behavior of objects in different situations.

3. How do you find the forces acting on a mass attached to a string?

To find the forces acting on a mass attached to a string, we use the principles of statics and apply them to the specific situation. This involves drawing a free body diagram, identifying all the forces acting on the object, and using equations to determine the magnitude and direction of each force.

4. What are the common forces acting on an object in equilibrium?

The common forces acting on an object in equilibrium include weight, normal force, tension, friction, and applied forces. These forces can either be balanced or unbalanced, depending on the object's state of equilibrium.

5. How can we ensure that an object is in equilibrium?

An object is in equilibrium when all the forces acting on it are balanced, meaning they cancel each other out. To ensure an object is in equilibrium, we need to make sure that the sum of all the forces acting on it is equal to zero. This can be achieved by adjusting the magnitude and direction of the forces or by changing the object's position.

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