Tensile and compressive forces

In summary, a tightrope walker uses static equilibrium to stay stable. The weight of the walker causes the line to deflect downward, and the tensile force in each half of the rope can be resolved into horizontal and vertical components. The two horizontal components are of equal magnitude and act in opposite directions, so their net force is zero. The sum of the vertical components of the tensile forces in the rope must equal the weight of the walker, and these components act in the opposite direction to the weight of the walker, so the net force in the vertical direction is zero. The sum of the forces in the horizontal and vertical directions is zero, so the walker is in static equilibrium.
  • #1
MBBphys
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Example of a tightrope walker:
Figure_04_05_06.jpg

Now, the weight force acts at a point. The rope is stretched. Compressive forces act inwards towards that point (opposite to TL and TR, the tensile forces). The resultant of the compressive forces equals the weight and is in the same direction – the weight force CAUSES the compressive forces.

If the man is stable on the tightrope and not moving, then resultant force is zero.

As string is stretched, tension forces act away from the point where weight acts (see image above). These are labelled TL and TR. The resultant of the tensile forces equals the weight in magnitude, but acts in the opposite direction, producing zero net force.

Is my understanding correct? Thanks in advance for your reply :)
 
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  • #2
MBBphys said:
Example of a tightrope walker:
Figure_04_05_06.jpg

Now, the weight force acts at a point. The rope is stretched. Compressive forces act inwards towards that point (opposite to TL and TR, the tensile forces). The resultant of the compressive forces equals the weight and is in the same direction – the weight force CAUSES the compressive forces.

What compressive forces? The wire is placed in tension by the weight of the walker.

You should know from experience that you can't push on a rope. Since you can't push on a rope, there is no compressive force.
If the man is stable on the tightrope and not moving, then resultant force is zero.
That is why it's called static equilibrium.
As string is stretched, tension forces act away from the point where weight acts (see image above). These are labelled TL and TR. The resultant of the tensile forces equals the weight in magnitude, but acts in the opposite direction, producing zero net force.

The weight of the walker causes the line to deflect downward. The tensile force in each half of the rope can be resolved into a horizontal and a vertical component.

For static equilibrium to occur, the sum of all these forces must equal zero.

The two horizontal components are of equal magnitude acting in opposite directions, so their net force is zero.
The sum of the vertical components of the tensile forces in the rope must equal the weight of the walker, and these components act in the opposite direction to the weight of the walker, so the net force in the vertical direction is zero.

The sum of the forces in the horizontal and vertical directions is zero, therefore, the walker is in static equilibrium.
 
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  • #3
SteamKing said:
What compressive forces? The wire is placed in tension by the weight of the walker.

You should know from experience that you can't push on a rope. Since you can't push on a rope, there is no compressive force.

That is why it's called static equilibrium.The weight of the walker causes the line to deflect downward. The tensile force in each half of the rope can be resolved into a horizontal and a vertical component.

For static equilibrium to occur, the sum of all these forces must equal zero.

The two horizontal components are of equal magnitude acting in opposite directions, so their net force is zero.
The sum of the vertical components of the tensile forces in the rope must equal the weight of the walker, and these components act in the opposite direction to the weight of the walker, so the net force in the vertical direction is zero.

The sum of the forces in the horizontal and vertical directions is zero, therefore, the walker is in static equilibrium.
Ah yes I get why I was wrong; thanks so much for your help :)
 

Related to Tensile and compressive forces

1. What is the difference between tensile and compressive forces?

Tensile forces act in opposite directions, pulling an object apart. Compressive forces act in the same direction, pushing an object together.

2. How are tensile and compressive forces measured?

Tensile forces are typically measured in units of force per unit area, such as pounds per square inch (psi) or newtons per square meter (N/m^2). Compressive forces are also measured in the same units.

3. What materials are most affected by tensile and compressive forces?

Most materials are affected by both tensile and compressive forces, but some are more susceptible to one type over the other. For example, materials like steel are stronger under compressive forces, while materials like rubber are stronger under tensile forces.

4. How do tensile and compressive forces affect the shape and structure of materials?

Tensile forces can stretch and elongate materials, while compressive forces can cause materials to compress and become shorter. Both types of forces can also cause materials to deform or break if they exceed the material's strength.

5. What are some real-life examples of tensile and compressive forces?

Some examples of tensile forces include stretching a rubber band, pulling on a rope, or hanging weights from a ceiling. Compressive forces can be seen when pushing on a door, stacking books on top of each other, or sitting on a chair.

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