Find the mass of the load, if it makes 20 vibrations in 16 seconds, the spring stiffness is 250n / m

n = 20.
t = 16 s.
k = 250 N / m.
m -?
The period of oscillation T of the frontal pendulum is the time of one complete oscillation. Since the pendulum makes n oscillations in time t, then the oscillation period is expressed by the formula: T = t / n.
The oscillation period of a spring pendulum is determined by the formula: T = 2 * P * √m / √k, where P is the number pi, m is the mass of the load, k is the stiffness of the spring.
t / n = 2 * P * √m / √k.
√m = t * √k / n * 2 * P.
The mass of the load of the spring pendulum will be determined by the formula: m = t ^ 2 * k / n2 * 4 * P ^ 2.
m = (16 s) 2 * 250 N / m / (20) ^ 2 * 4 * 3.14 ^ 2 = 4 kg.
Answer: a weight of mass m = 4 kg is attached to the spring.