As we know total momentum of a system is constant according to law of conservation of momentum i.e.
where m indicates mass and v indicates velocity .
Now initial mass of system = 10 +2= 12 kg;
initial velocity = 2m/s ( assuming south as positive direction)
initial momentum = 12 ×2 = 24kgm/s;
Now, after jump
Final momentum = 2v - 10(-1)= 2v-10 ;
according to law
Final result is :-
velocity of the hoverboard = 17m/s in south.