It could never actually happen like this, but the question is looking for you to 'conserve' the momentum.
Momentum of a moving object is (mass) x (velocity). Like velocity, momentum has a direction. Momentum is one of those things that's 'conserved'. That means that momentum can't appear out of nowhere, and it doesn't disappear. The total after the collision is the same as the total was before the collision.
Momentum of the skinny player:
(70 kg) x (3 m/s north) = 210 kg-m/s north.
Momentum of the heavy player:
(80 kg) x (1.5 m/s south) = 120 kg-m/s south .
Total momentum before the collision is
(210 kg-m/s north) + (120 kg-m/s south)
= 90 kg-m/s north .
It has to be the same after the collision.
(mass) x (velocity) = 90 kg-m/s north.
The mass after the collision is 150 kg, because they get tangled up and stuck together, and they move together.
(150 kg) x (velocity) = 90 kg-m/s north .
Divide each side by 150 kg : velocity = (90 kg-m/s north) / (150 kg)
You could heat the syrup, grease the spoon with shortening, because if you do, then the molasses won't stick when you pour it out of the spoon into the batter.
