# Action and Reaction - Time lag

Is there a time lag between action and reaction ? If there isn't such a time lag, the reaction force must cancel the applying force although they act on different bodies.

My second question is that,

Does the collision time $\delta$t depend on the colliding masses and their velocities ?

• How they cancel one another if they act on different bodies? – Sofia Dec 20 '14 at 17:23
• Echoing @Sofia's comment: physics.stackexchange.com/q/45653/2451 – Qmechanic Dec 20 '14 at 17:51
• Are you asking for the theoretical answer in Classical Newtonian physics, or the current most accurate real-world answer which would necessarily involve relativity? Relativity implies that certain kind of changes in one system (like the acceleration of a charged object) can't result in a changed force on another system until there's been time for some sort of signal to travel at the speed of light from one to the other. – Hypnosifl Dec 20 '14 at 23:08

The mass and velocity of colliding objects plays very little role on the impact time $\delta t$ during an elastic collision although it can matter during an inelastic collision.