Are we making your homework ?

We have a mass and a force (actually a resistance, but that amounts to the same thing). We can calculate the accelaration (because it is a negative force, the acceleration will be negative, too).

Force = mass * acceleration or

acceleration = force / mass = 100 N / 0.01 kg = 10000 m/sec^{2}

Now we cheat a bit, and make the movement in reverse. We start with speed zero, and accelerate till we are out of the target.

When starting from zero, the distance covered is

(1/2)*acceleration*time^{2}

distance is 0.08 m; acceleration is 10000 m/sec^{2}

time^{2} = (0.16m)/(10000m/sec^{2}) = (16/1000000)sec^{2}

time = 4/1000 sec

speed = (0.004 sec)*(10000 m:sec^{2}) = 40 m/sec

This must be equal to the speed at impact.