Two pucks moving on a friction less air table are about to collide. The 1.5 kg puck is moving directly east at 2 m/s. the 4 kg puck is moving directly north at 1 m/s. What is the total kinetic energy of the two-puck system before the collision?

a) sqrt(13) J
b)5 J
c)7 J
d)10 J
e)11 J
I got b) as the answer by using KE=1/2 mv^2 of both of the pucks. Then I added the two numbers up and got b).

(1/2)[(1.5x4) + (4x1)] = 5
You got it!