A 1 260 kg car traveling initially with a speed of 25.0 m/s in an easterly direction crashes into the back of a 8 000 kg truck moving in the same direction at 20.0 m/s. The velocity of the car right after the collision is 18.0 m/s to the east. (a) What is the velocity of the truck right after the collision? ( i got 21.10 as my vt)...using this:m(c) . v(c) + m(t) . v(t) = m(c) . V (c) + m(t) . V(t) m/s east (b) What is the change in mechanical energy of the car–truck system in the collision? (Use input values with an adequate number of significant figures to calculate this answer.) (for part be i was using the formula: (1/2)m1(v1^2) + (1/2)m2(v2^2)-(1/2)m1(v1^2) + (1/2)m2(vt)^2, and i got my answer as 8790, then it said my sign was wrong, and made it to -8790, and its still wrong)....does anyone know how to do this problem?