And.. where is the rest of the question?
Hooke's Law
F = k. Δx
Δx = 30 cm = 0.3 m
200 = k . 0.3

the spring stretch for 100 N:

The speed is 10.5 miles per minute, or 630 miles per hour.
We don't know the velocity, because you didn't tell us anything about the direction I'm going.
Gamma-rays, the explanation and information is found in the image below.