1. The problem statement, all variables and given/known data Small object A (mass: [m][/A]) is travelling in a linear path on a horizontal surface and collides elastically with small object B ([m][/B]), at rest on the same line, with a speed of v. Friction between the objects and the horizontal surface is negligible. What is the impulse imparted to A by B during the collision? The positive direction of impulse is defined as the direction of A's velocity before collision. Correct answer is 1. 2. Relevant equations Impulse = mdv v - 0 = [v][/B] - [v][/A] and maybe [m][/A]v = [m][/B][v][/B] + [m][/A][v][/A]? 3. The attempt at a solution Isn't the impulse simply -[m][/A]v? Since collision was elastic, change in velocity be v - 0 = v. The direction would be towards the negative because [m][/A] would be moving in the opposite direction after collision.