
Answer:
The length of cable is 12.5 m
Explanation:
Since, the wrecking ball completes 1 oscillation, in the same time, as it takes for the rock to complete 5 oscillations.
Therefore,
Time Period of Wrecking Ball = 5 (Time Period of Rock)
Since,
Time Period of  Pendulum = 2Ďâ(L/g)
Therefore,
2Ďâ(Lâ/g) = 5[2Ďâ(Lâ/g)]
âLâ = 5âLâ
Squaring on both sides:
Lâ = 25 Lâ
where,
Lâ = Length of Cable = ?
Lâ = Length of string = 0.5 m
Therefore,
Lâ = 25 (0.5 m)
Lâ = 12.5 m