Im preparing for an Elastic Collision lab today and was wondering is someone would check my prelab questions. A 5 kg object traveling at 4 m/s collides head on with a 10 kg object moving toward it with a speed of 3 m/s. The 10 kg object stops dead after the collision. a) What is the final speed of the 5 kg object? I used conservation of momentum. p1i + p2i = p1f + p2f 20 - 30= p1f + 0; p1f= -10; v1f= -2 m/s b) Is the collision elastic? This is where i question myself. Since the lab is for an elastic collision I would think it would be elastic. However, when I plug these values into their KE values it seems otherwise. KE1i + KE2i = KE1f + KE2f (.5 * 5 * 16) - (.5 * 10 *9) = (.5 * 5 * 4) + 0 Since 40 - 45 = 5; and KE1f = 10; It is inelastic. Right?