(20 1 1? Xiantao) This year, the middle and lower reaches of the Yangtze River suffered the longest drought in 50 years, and all localities were pumping water to fight drought. The picture shows a vil

(20 1 1? Xiantao) This year, the middle and lower reaches of the Yangtze River suffered the longest drought in 50 years, and all localities were pumping water to fight drought. The picture shows a village pumping water to fight drought. (1) ∫ P0 = rho water gh,

∴ Maximum height of pump shaft from water surface:

H=p0ρ water g =1.01×105pa1×103kg/m3×10n/kg =10./kloc.

(2) Useful work done by mechanical device 1 hour:

W useful =GH

= ρ water vgH

= 1× 103kg/m3× 180 m3× 10N/kg× 12m

=2. 16× 107J，

Useful power:

P Yes =W useful t = 2.16×107j3600s = 6000 w;

(3)3) 1.25 liters of heat generated by complete combustion of diesel oil:

Q amplifier =qm

=qρ diesel v diesel

= 4× 107j/kg×0.8× 103kg/m3× 1.25× 10-3 m3

=4× 107J，

Efficiency of the whole mechanism:

η=W Useful Q amplifier ×100% = 2.16×107j4×107j×100% = 54%.

Answer: (1) The maximum height h between the pump axis and the water surface is10.1m;

(2) The power of useful work done by this mechanical device is 6000 W；;

(3) The efficiency of the whole mechanical device is 54%.