The SI unit of force is newton which is equal to             

The S.I unit of force is newton

1 newton $=1{\text{kgms}}^{-2}$  

Because the formula for force F is

F = ma

m is mass, a is acceleration

Unit of mass -1kg

Unit of acceleration - ${\text{m/s}}^{\text{2}}$

$\therefore 1\text{newton}=1\text{kg}{\text{m/s}}^{\text{2}}$

$=1\text{kg}{\text{ms}}^{-2}$