Our old clock is battery-powered and the capacity of the battery is E=1.2Wh. The hour hand is rh=5cm long and the minute hand is rm=8cm long. The linear density of each hand is τ=10g⋅m−1. The efficiency of the clockwork is η=7%. How long does it take for the clock to stop? The hands rotate continuously and any potential energy released during descending is lost.