Physics Torque Equilbrium Question

  • #1
singh101
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Homework Statement
I can't seem to figure out this question. I would greatly appreciate any help. I have attached a photo of the question. Thank you!
Relevant Equations
Torque=Ia
Torque= radius x Force
IMG_4940-2.jpg
 
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  • #2
Carefully write the "sum of torques equals zero equation " for this problem. Don't forget to include the torque from the normal reaction from the part of ground that supports the plank and the two torques from the weight of the plank of its two different parts (one will be positive and the other negative).

Which Torque becomes zero (except from the total torque) when the plank is about to start tip over?
 
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  • #3
sorry I am a little confused is their anyway you can show this on a piece of paper?
 
  • #4
I am not going to solve the problem for you, you got to show some effort. You got to write a post with some equations that you think are the solution to the problem and then we can talk further.
 
  • #5
the problem is I don't know what to write for the R for the torque acting on the left side of the beam. I know the Force will be MxG which is 40 x 10= 400 so that lead me to write 400(r)-500(r)=0 The answer we are trying to find is the r which relates to the 50. But I am confused on what the r should be for the 40.
 
  • #6
Ok that's a start.

The -500r term is correct and is the torque from the weight of the kid.
The 400r term is not correct for multiple reasons.
Don't you think that first we should "break" the torque from the weight of the plank into two terms one positive and one negative?
 
  • #7
Attached below is the answer key. I understand how to set up the equation and solve the question. But the part which confused me is the 1.5 which is right next to Mg. My question is why is the 1.5 length used rather than the entire length of 4.5 on the left side. I seem to get stuck on that portion of the question.
IMG_4943.jpg
 
  • #8
OK I see the answer key solves it in a slightly different way than what I had in mind but it is correct.

What is the center of mass (or center of gravity) of the plank?
 
  • #9
I am think its the orange spot on beam right next the child.
 
  • #10
The picture doesnt show so clearly here, so i cant see any orange spot.

But for a moment lets say you have a plank of homogeneous mass density of length 6m. At which distance along the plank is located the center of mass?
 
  • #11
3 m?
 
  • #12
Correct. Now you should know that the torque of weight acts like the weight is totally concentrated on the center of mass of the plank . I mean its like the plank is weightless and you have another kid with weight 40kg sitting at the center of mass of the plank.

That is a theorem in classical mechanics about the torque of the weight of a continuous mass distribution under constant gravitational acceleration.
 
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FAQ: Physics Torque Equilbrium Question

What is torque in physics?

Torque, also known as the moment of force, is a measure of the rotational force applied to an object. It is calculated as the product of the force and the distance from the point of rotation, typically represented as τ = r × F, where τ is the torque, r is the lever arm (distance), and F is the force applied.

How do you determine the direction of torque?

The direction of torque is determined by the right-hand rule. If you point the fingers of your right hand in the direction of the lever arm and curl them toward the direction of the force, your thumb will point in the direction of the torque. Clockwise torque is considered negative, and counterclockwise torque is considered positive.

What is torque equilibrium?

Torque equilibrium occurs when the sum of all torques acting on an object is zero, resulting in no net rotational acceleration. This means that the clockwise torques balance the counterclockwise torques, keeping the object in rotational equilibrium.

How do you solve a torque equilibrium problem?

To solve a torque equilibrium problem, follow these steps: (1) Identify all the forces acting on the object and their points of application. (2) Choose a pivot point for calculating torques. (3) Calculate the torque produced by each force about the pivot point. (4) Set the sum of clockwise torques equal to the sum of counterclockwise torques. (5) Solve the resulting equation for the unknown variable.

What are common applications of torque equilibrium?

Common applications of torque equilibrium include balancing seesaws, determining the forces on beams in structural engineering, analyzing the stability of objects, and understanding the mechanics of levers and pulleys. Torque equilibrium principles are crucial in designing and analyzing mechanical systems to ensure they function correctly and safely.

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