Answer:
v = 6.283 m/s
Step-by-step explanation:
Given:
mass of the object, m = 1.00kg
The next time the speed is zero is at t = 0.200s i.e the one half of a total oscillation.
thus,
The time (T) for one complete oscillation will be = 2 × 0.200s = 0.4s
Now,
we know time period (T) is given as:

where, k is the spring constant
substituting the values in the above equation we get

or

or
k = 246.70 N/m
Then, using the concept of conservation of energy, we have

where,
x is the displacement in the spring
v = speed of the object
substituting the values in the above equation we get

or

or
v = 6.283 m/s (Answer)