Block 1, of mass m1=1.50 kg, moves along a frictionless air track with speed v1=31.0m/s. It collides with block 2, of mass m2=39.0 kg, which was initially at rest. The blocks stick together after the collision. 

A: Find the magnitude pi of the total initial momentum of the two-block system. Express your answer numerically. 

B: Find vf, the magnitude of the final velocity of the two-block system. Express your answer numerically. 

C: what is the change deltaK= Kfinal- K initial in the two block systems kinetic energy due to the collision ? Express your answer numerically in joules.