v^2-v0^2=2as → 2.0^2 m/s - 0 m/s=2a . 2.0 m → a=1 m/s^2

F=m.a → 4.0 N = m . 1.0 m/s^2 → m=4.0 kg

I have corrected it now.

u=2.0ms-1

v=0

s=2.0m

v^2-u^s=2as

0-4=2a*2
-4/4=a
a = -1ms-^2
Force = mass*accelaration

Since, force is resistive it will be negative

-4N= mass*-1ms^-2

-4N/-1ms-^2=mass

mass=4 Kg

you took initial velocity as 0 whereas final velocity should be zero

the expression is v^2 -u^2 =2as

where v is final velocity and u is initial velocity

Thank you so much .

No difference which one is initial and which is final. You end op with a positive number for the mass as we use the absolute values for all parameters.

Have you got two different values for acceleration?!

One in newtons and one in m/s^2?!

And what about the mass which is the question

Oh sorry I didn’t notice, it was a typo I corrected it