two particles of mass m1=1.5 kg, and m2=3.5 kg undergo a 1-dimensional head-on collision. Their velocities along x are V1i=12 m/s, and V2i=-7.5 m/s. The 2 particles stick together after the collision. a.) Find the velocity after the collision. b.) How much kinetic energy is lost in the collision?

Question

two particles of mass m1=1.5 kg, and m2=3.5 kg undergo a 1-dimensional head-on collision. Their velocities along x are V1i=12 m/s, and V2i=-7.5 m/s. The 2 particles stick together after the collision. a.) Find the velocity after the collision. b.) How much kinetic energy is lost in the collision?
 I used p for m1=18, and p for m2=-26.25, with a total system momentum of p=-8.25.
-8.25=1.5+3.5v
-8.25/5=  v=-1.65 m/s.
Using KE=1/2mv^2, I calculated Kf to be -4.125, but then also calculated that Ki =-4.125.
Does this mean that there is no KE lost during the collision?

bobpursley · Answer

KE after: 1/2 1.5(1.65^2)+1/2*3.5*(1.65^2)=13.6/2 Not your resulet.