Tension force is attractive.
Tension is fundamentally caused by the attractive forces acting between the particles within an object as it is stretched or pulled. When you exert force on an object, like a rope or cable, attempting to pull its ends away from each other, the internal particles resist this separation. This resistance arises from the electromagnetic forces that hold the atoms and molecules of the material together.
As stated in the provided reference, "Tension is caused by attractive forces between particles as they are pulled apart." This means that the force within the material acts to pull the particles back together, opposing the external pulling force.
Understanding Tension
Imagine a rope being pulled from both ends. Each segment of the rope is pulling on the adjacent segments towards the centre of the rope, essentially trying to keep the material intact. This internal pulling force is the tension.
- Attractive Nature: The forces between the particles (atoms/molecules) act like tiny springs pulling the particles towards each other. When stretched, these "springs" are extended, and they exert a restoring force that is attractive, attempting to return to their equilibrium positions.
- Direction of Force: Tension acts along the direction of the object (like a rope or wire) and away from the point of application, pulling inwards on the object it is connected to.
How Tension Contrasts with Repulsive Forces
While tension is attractive, other forces like normal contact forces are repulsive.
| Force Type | Cause | Nature | Example |
|---|---|---|---|
| Tension Force | Attractive forces between pulled particles | Attractive | Pulling on a rope; cable supporting a lift |
| Normal Force | Repulsive forces between compressed particles | Repulsive | A book resting on a table |
As the reference also notes, "Normal contact forces are caused by the repulsive forces as particles are pressed under an object's weight." When objects are pressed together, the electron clouds of their surface atoms repel each other, creating the normal force. This is the opposite nature to the attractive forces that cause tension.
Practical Examples of Tension
Tension is a common force in everyday life and engineering:
- Ropes and Cables: When lifting an object with a crane, the cable experiences tension. The cable's internal attractive forces prevent it from breaking as it is stretched by the load's weight.
- Bridges: Suspension bridges use massive cables under tension to support the weight of the bridge deck.
- Musical Instruments: The strings on a guitar or piano are under tension. Plucking them causes them to vibrate, producing sound.
- Tug-of-War: The rope in a tug-of-war game is under significant tension as teams pull from opposite ends.
In each of these cases, the material is being pulled or stretched, and the tension force within acts to resist this pulling, a manifestation of the internal attractive forces holding the material together.
Key Takeaway
Based on the physical principles and the provided reference, tension force is distinctly attractive, stemming from the internal attractive forces of the material resisting separation.
