That depends on how fast you want the speed to change from 10 m/s to 20 m/s. This is just another way of saying "what you want the acceleration to be".
F = m A
Force = (mass) x (acceleration)
If you want the speed to change from 10 m/s to 20 m/s in 1 second, then
Force = (20 kg) x (10 m/s²) = 200 Newtons
If you can wait a whole day for the speed to change gradually, then
Force = (20 kg) x (10 m/s)/(86,400 sec) = 0.00231... Newton
-- 1000 Newtons will complete the change of speed in 0.2 second
-- 3000 Newtons will complete the change of speed in 0.067 second
-- 4000 Newtons will complete the change of speed in 0.05 second
-- 100 Newtons will complete the change of speed in 2 seconds
Even if you KNOW the required acceleration, none of the choices on the list can be the correct force, because ' j ' is not even a unit of force.
