Impulse

[nokia8650]

If body A exerts an impulse of say +2Ns on B, then does body A exert an impulse of -2Ns on B providing no external forces act?

Thanks

[RoyalCat]

Consider the definition of impulse, newton's third law and preservation of momentum.

J12 = F12*dt
J21 = F21*dt
dt is the same for both impulses, since the bodies remain in contact for a set time, which is equal for both of them.

F12 = -F21 (Newton's third law)
Therefore:
J12 = -J21
Jtot = J12+J21 = 0
Which makes perfect sense when you consider:
J = dP
The momentum of a system remains constant if no external forces act on that system.