6.10
张力
View the full transcript and gain access to JoVE Core videos
Q1: What is tension and why can it only pull and not push?
Tension is the force carried by a flexible medium like a rope, cable, or string. It acts parallel to the connector's length and can only pull outward along the two ends; you cannot push a rope. This pulling force is transmitted through the flexible connector to attached objects, making it fundamentally different from forces that can both push and pull.
Q2: How does tension get transmitted through a flexible connector without changing magnitude?
When there is no friction, tension transmits undiminished through a flexible connector. Only the direction of the force changes as it follows the connector's path, but the magnitude remains constant. This principle applies to tendons in fingers and bicycle brake cables, which redirect muscle and hand forces to other parts without losing strength.
Q3: How do you calculate tension forces on an object pulled at an angle?
When a box is pulled by a string at an angle on a smooth surface, resolve tension into x and y components. The x-component acts horizontally, while the y-component acts vertically alongside the normal force and weight. Apply Newton's second law to each direction separately to find the tension force and normal force exerted on the object.
Q4: What forces act on an object suspended by a rope in equilibrium?
An object suspended by a rope experiences three forces: gravitational pull downward, normal force upward from the surface, and tension force along the rope. In equilibrium, tension balances the weight of the object. Understanding these force interactions is essential for analyzing first law particles in one dimensional equilibrium scenarios.
Q5: Why are flexible connectors used in mechanical systems like brake cables?
Flexible connectors like brake cables transmit forces around corners and through complex paths without losing magnitude. They redirect force direction while preserving strength, making them ideal for systems requiring force transmission through tight spaces. Tendons in fingers similarly carry muscle forces while changing direction but maintaining magnitude.
Q6: What is the relationship between tension and the word tendon?
The word tension comes from Latin meaning to stretch. Flexible cords that carry muscle forces to other body parts are called tendons, reflecting this etymological connection. Like ropes and cables, tendons are relatively friction-free connectors that transmit pulling forces parallel to their length.