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一、境空题 1.40瓦=__焦/秒=__牛·米/秒=__千瓦. 2.一台拖拉机的功率是9×10~3瓦,表示的物理意义是__. 3.水桶掉入井中,从井里捞水桶时,桶内带了一些水,则人对水做的功是__功,对桶做的功是__功.桶内水越少,桶的机械效率__. 4.骑自行车上桥时,常走成S形以省力,这是因为__,这样做虽然省力,但____. 5.用一个重8牛的动滑轮提升100牛的重物,至少需__牛的力,若重物被匀速提升40厘米过程中,绳自由端拉力做功50焦,则该滑轮组的机械效率为__.
First, the air space problem 1.40 watts = __ coke / second = __ cattle meters / second = __ kilowatts. 2. The power of a tractor is 9 × 10 ~ 3 watts, said the physical meaning is __. 3 When a bucket falls into a well and a bucket is drawn from the well, some water is carried in the bucket, then the work done by man on the water is __ work, and the work done on the bucket is __ work. Mechanical efficiency __ 4. riding a bike on the bridge, often go into the S-shaped to save effort, it is because __, although labor-saving, but ____ 5. with a heavy 8-cow pulley to enhance the weight of 100 cattle , At least __ cattle force, if the weight was uniform 40 cm in the process of lifting the rope to do the work of the free end of the tension 50 coke, then the mechanical efficiency of the pulley group __.