Physics
posted by Rachel on .
A barge with mass 1.7×105 kg is proceeding down river at 6.1 m/s in heavy fog when it collides broadside with a barge heading directly across the river. The second barge has mass 2.83×105 kg and was moving at 4.2 m/s. Immediately after impact, the second barge finds its course deflected by 18° in the downriver direction and its speed increased to 5.0 m/s. The river current was practically zero at the time of the accident. What are the speed and direction of motion of the first barge immediately after the collision? a)Speed?
b)Enter the angle of deflection from the original direction with + as motion to its left and  as to its right.
c)How much kinetic energy is lost in the collision?

Use the law of conservation of momentum to solve this. Since that is a vector, do it in both directions (crossways).

I used the equation m1vfm1vi=m2vf+m2vi and got a velocity of 4.77m/s but that answer is incorrect.
Am I not using the right formula for question (a)? 
ok i figured out what I did wrong for the (a). I also found (b). But I cannot seem to get the right answer for the kinetic energy lost in the collision.

how do you do part a?