Junior high school science requires writing formulas, In order to reduce urban air pollution, Shenzhen municipal government encourages citizens to use electric bicycles. The technical parameters of an electric bicycle are as follows: 1. Motor 36V, 180W 2. Sealed maintenance free lead acid battery (12V, 12a) x3 3. The rated load is 75kg and the maximum speed is 20km / h 4. It can drive 60km at normal speed of 15km / h 5. Charging power consumption is 1.2kw/h when driving 100km (1) How much work does an electric bicycle do to overcome the resistance when it runs at a normal speed (15km / h) with a resistance of 24N? (2) What is the mechanical efficiency of the electric bicycle?

Junior high school science requires writing formulas, In order to reduce urban air pollution, Shenzhen municipal government encourages citizens to use electric bicycles. The technical parameters of an electric bicycle are as follows: 1. Motor 36V, 180W 2. Sealed maintenance free lead acid battery (12V, 12a) x3 3. The rated load is 75kg and the maximum speed is 20km / h 4. It can drive 60km at normal speed of 15km / h 5. Charging power consumption is 1.2kw/h when driving 100km (1) How much work does an electric bicycle do to overcome the resistance when it runs at a normal speed (15km / h) with a resistance of 24N? (2) What is the mechanical efficiency of the electric bicycle?

（1）W=FS=24*100000=2400000J
(2) Wtotal = 1.2 * 3600000 = 4320000j mechanical efficiency = 2400000 / 4320000 = 0.56