Tension and normal force are distinct forces, and tension does not directly affect normal force.
The statement from the reference is quite clear: "Tension is just a pulling force that a rope gives to the object it is attached to. It has nothing to do with normal force. the force with which the block pulls the force back can be called normal which even though will have magnitude of tension as per newtons third law they are different." This means that while both forces might exist in a single system, they are independent of each other.
Understanding Tension and Normal Force
Let's break down each force to understand their differences:
-
Tension:
- Tension is a pulling force transmitted through a string, rope, cable, or similar object when it is pulled tight by forces acting from opposite ends.
- It acts along the length of the rope or cable.
- Tension forces pull objects that are connected by ropes, etc.
-
Normal Force:
- The normal force is a contact force exerted by a surface on an object.
- It acts perpendicular to the surface.
- It represents the force that opposes the weight of an object pressing down on the surface.
The Key Difference: Interaction Type
The crucial distinction is that tension is a force within a cable pulling on an object, whereas normal force is a force from a surface pushing against an object. They are fundamentally different types of forces arising from different interactions, and so tension does not affect normal force.
Examples
| Scenario | Tension | Normal Force |
|---|---|---|
| A block being pulled by a rope across a table | Exists in the rope, pulling the block forward. | Exists between the table and block, pushing up on the block. |
| A block hanging vertically from a rope | Exists in the rope, pulling the block upwards. | Normal force is zero since there is no contact with a surface. |
| A block resting on an inclined plane, with a rope parallel to the inclined plane but slack | No tension when rope is not pulling. | Exists between the plane and the block perpendicular to the plane's surface. |
| A block resting on an inclined plane being pulled up the incline. | Exists in the rope, pulling the block up the plane | Exists between the plane and the block perpendicular to the plane's surface. |
Newton's Third Law and the Misconception
The reference also mentions Newton's third law, which may create some confusion.
- While the magnitude of the tension in a rope can sometimes equal the magnitude of the normal force acting on the object, particularly in very specific scenarios (like a hanging block being held up by a rope when the rope is under tension), these forces are still distinct.
- The tension acts on the block via the rope, while the normal force acts on the block because of the surface it is on.
- It is important to remember that Newton's third law involves pairs of forces acting on different objects, so while the pulling force on a rope is related to the force of the rope on the object, those forces act on different objects.
Conclusion
In conclusion, tension and normal force are not directly related, although both may exist in a similar situation. Tension is a pulling force through a rope, while normal force is a pushing force exerted by a surface. The magnitude of one does not affect the magnitude of the other.
