Well to find the answer for force, the formula is mass X acceleration.
So, 20m/s² X 0.5kg = 10kg-m/s².
But, because we measure force in Newtons, we have to change the units (kg/m/s²) to Newtons.
1N (newton) equals to 1kg-m/s² and because we had 10, your answer is
10N
