Find the quality factor of a mathematical pendulum l=l=l= =50 cm=50 \mathrm{~cm}=50 cm long if during the time interval τ=5.2 min\tau=5.2 \mathrm{~min}τ=5.2 min its total mechanical energy decreases η=4.0⋅104\eta=4.0 \cdot 10^{4}η=4.0⋅104 times