[SOLVED] Two carts with masses of 8.0 kg and 1.8 kg, respectively, move on a friction 1. The problem statement, all variables and given/known data Two carts with masses of 8.0 kg and 1.8 kg, respectively, move on a frictionless track with velocities of 8.0 m/s and 3.5 m/s. The carts stick together after colliding head-on. Find the final speed. 2. Relevant equations m1v1+m2v2 = v (m1 + m2) v_final = (m1*v1 + m2*v2)/(m1+m2) 3. The attempt at a solution (8*8)+(1.8*3.5)=70.3 so 70.3=(8+1.8)V which is then 70.3=9.8V V=7.17 but it says i'm doing it wrong. (webassign problem) please show me how i did it wrong?? or whats wrong?