Simple FBD problem: person, chair, earth

  • Thread starter bobthebanana
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    Earth Fbd
In summary, when a person is sitting on a chair, there are multiple forces at play. The chair and the person exert forces on each other due to their mutual attraction according to Newton's law of Universal gravitation. The weight of the total system acts downwards on the Earth, which in turn exerts an equal and opposite force on the chair to keep it in place. These forces must be balanced in order for the chair to remain on the Earth. Additionally, the Earth and the chair also form a third law pair, with the Earth attracting the chair and the chair pressing into the Earth in response.
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bobthebanana
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Homework Statement


A person is sitting on a chair. Draw force diagrams for the person, the chair, and the earth.


Homework Equations


Identify the third law pairs too, por favor.


The Attempt at a Solution


attached GIF is my attempt. what forces do i draw on the earth

thanks for the help
 

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  • #2
reply :zzz:
 
  • #3
In order for the chair to remain on the earth, the net force on the chair (with respect to the earth) must be zero. The weight of the total system is acting downwards on the Earth and the Earth is exerting a equal but opposite force.
 
  • #4
The Earth attracts the person and the chair (albeit separately!) and vice versa according to Newton's law of Universal gravitation. Since the chair presses into the Earth (due to its attraction by the Earth and the weight of the person sitting on it) it responds with a force of similar magnitude acting in the opposite direction on the chair (real forces always comes in pairs).
 

1. What is a simple FBD (Free Body Diagram) problem?

A simple FBD problem involves representing the forces acting on an object in a diagram, with the object being represented by a dot and the forces as arrows. This helps to visualize and analyze the forces acting on the object.

2. How do you draw a simple FBD for a person sitting on a chair on Earth?

To draw a simple FBD for a person sitting on a chair on Earth, you would first draw a dot to represent the person and a dot to represent the chair. Then, you would draw arrows to represent the forces acting on the person, such as the force of gravity pulling the person towards the center of the Earth and the normal force from the chair pushing back up on the person.

3. What is the significance of a simple FBD in problem-solving?

A simple FBD allows you to break down a complex problem into smaller, more manageable parts. By visually representing the forces acting on an object, it helps to identify which forces are balanced and which are unbalanced, making it easier to solve the problem.

4. How do you determine the direction of the arrows in a simple FBD?

The direction of the arrows in a simple FBD is determined by the direction of the force. For example, if the force is pushing an object to the left, the arrow representing that force would point to the left.

5. Can a simple FBD be used to solve problems in other areas of science?

Yes, a simple FBD can be used to solve problems in other areas of science, such as physics, engineering, and even biology. It is a useful tool for analyzing the forces acting on an object in any given situation.

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