什麼因素會影響碰撞時間的長短?

質量被考慮為碰撞時間的因素是因為，牛頓的物理定律：物體的質量越大，就越難被移動。簡單說就是被撞擊者的重量越大，越難被撞移位，或只會輕微移位，就越會縮短碰撞時間的長度。

第二、撞擊物本身的性質，例如是海綿、容易破碎的物件等，那麼就會延長碰擊時間，從而大大減低兩者的受損程度。

物件重量,同埋velocity(speed with direction),because
衝力=重量 x velocity
重有佢係咩表面上碰撞(e.g.滑既table)
同一物質碰撞前的速度愈快，碰撞時間will be shorter because the force repel.

It depends on the elasticity of the objects and the velocity of impact.

Just think of the situation of an object moving towards and colliding with a spring. The time of contact of the object with the spring before rebounding to leave contact with the spring will then depends on the [spring constant] (i.e. its elasticity) and the impact velocity.

You may therefore assume that in the colliding process, there is an [imaginary spring] exists between two colliding objects.

2007-03-30 15:53:26 補充：
Sorry...I made a mistake. The time of impact actually depends on the elasticity of the material and the MASSES of the colliding objects, but NOT on the velocities of the objects. The impact time increases with the mass of the objects and decreases with the elasticity.