Find the length of the thread of a pendulum that makes 40 oscillations in 1 minute.

These tasks: t (duration of oscillations of the pendulum) = 1 min (in SI t = 60 s); n (number of vibrations) = 40 vibrations.

Reference values: g (acceleration due to gravity) = 9.81 m / s2.

To determine the length of the pendulum thread, we use the equality: t / n = T (period) = 2 * Π * √ (l / g), whence √ (l / g) = t / (n * 2Π); l / g = t ^ 2 / (n ^ 2 * 4Π ^ 2) and l = t ^ 2 * g / (n2 * 4Π ^ 2).

Let’s make a calculation: l = 60 ^ 2 * 9.81 / (40 ^ 2 * 4 * 3.14 ^ 2) = 0.56 m.

Answer: The length of the pendulum thread is 0.56 m.