A 0.118 kg mass is moving horizontally with a speed of 8.49 m/s when it strikes a vertical wall. The mass rebounds with a speed of 1.07 m/s. What is the magnitude of the change in linear momentum of the mass? isn't the change just the difference in momentum? I did .118(8.49 - 1.07) to get .87556 kg m/s. this is wrong so i think the answer is .118(8.49+1.07) because it would be minus a negative velocity. so i got 1.128 kg m/s. but i don't know if this number should be negative or not.