题干

深圳中集集团有限公司要用集装箱运输一批饮料到距三水港l26km的肇庆某码头.货船未装载货物时排开水的质量是400t.把总质量为600t的集装箱装载上船后,货船以7m/s平均速度驶向肇庆码头,船到码头后用如图所示的起重机把质量为20t集装箱吊起,(g=10N/kg)求:

(1)货船从三水港到达肇庆需要多长时间?

(2)若忽略滑轮和绳的质量及所有阻力,则电动机提供的拉力至少是多少?

(3)装载货物后,货船排开水的体积是多少?

(4)已知集装箱的长10米,宽3米,求此集装箱对轮船的压强?

上一题 下一题 0.0难度 选择题 更新时间:2016-08-19 11:04:01

答案(点此获取答案解析)

解:(1)由v=
s
t
可得:t=sv=126000m7<

同类题4

       Fashions in child-care (儿童保育), as all parents know, come and go. Bottle-feeding or mother's milk?  Full-time parental care or a child-minder(儿童保育员)? These problems always trouble the parents a lot. And now, there is a book called Childsplay dealing with the problem of child-care.
     The author of Childsplay, Lucy Jackson, believes most school children do some sports at school. And many adults take regular exercise in their free time.
      Babies, though, spend most of the time in front of the television or sitting in a push-chair (折叠式婴儿车) or high chair. If the world were a safer place, every child would run around freely, but that is simply not possible. As a result, they become lazy, overweight and unfit.
     Ms. Jackson is worried that if small children take no regular exercise, bad habits will continue into adulthood (成人期 ). She suggests that parents should begin exercising with very small babies, moving their legs and arms gently in time to music. As children grow, they should follow and exercise program using soft balls, household furniture and play equipment.                                    
     Many experts in child development do not agree. They feel that children will learn to run and jump as they play naturally; they do not need planned exercise. They would not be overweight if they ate healthier food. An increasing number of parents, though, are taking their children to exercise classes. The kids jump around with their mothers to disco music.They seem to enjoy themselves, but it is not at all clear if the classes have any effect on their future development.