momentum = velocity mass
= 5850 lb 70 ft/s
= 409500 lbft/s
these are rather odd units - converting everything to STI units first would make for a much nicer result:
70ft/s = 21.3 m/s
5850 lb = 2653.5 kg
therefore:
momentum in kgm/s=
21.3 m/s 2653.5 kg = 56520 kgm/s