Physics education research, electronic materials, and the musings of Christopher Moore, Ph.D.

A hunter has a rifle that can fire .06kg bullets with a muzzle velocity of 900m/sec. A 40 kg leopard springs a him at a speed of 10m/sec. How many bullets must the hunter fire into the leopard in order to stop him in his tracks?

i think just use .06kg(900m/sec) + 40kg(-10m/sec) = 40.06kg(V2)
                     V2 = -8.6m/sec
                     .06kg(900m/sec) + 40.06kg(-8.6m/sec) = 40.12kg(V2)
                    V2 = -7.2m/sec
                    etc..
until its 0 or less? i got 8 bullets (rounded up) doing so, is that wrong?