sisley0522
1. A cart on a horizontal track is moving to the left. Can the cart's acceleration be directed to the right? Explain your answer.A:yes,the acceleration of a body is not relate to it's motion but it's state of force.2. Newton's Second Law of Motion can be expressed as F=ma. Is ma a force? Explain your answer.A:no,ma is the result of the force3. Two boxes B1 and B2 are in contact with one another on a horizontal table. They are accelerated to the right by Homer's hand H. Identify the forces acting in the horizontal direction on H, B1, and B2 and determine which is the largest. Ignore air resistance and friction.A:can't understand the action
红月光薇儿
第一题是压强的，一个潜水员潜到20米深的水中，潜水员脸的直径是16厘米。问他的脸受多少力，解：F=ps=ρgh*s=1000*9.8*20*π*0.08^2=3939N第二题是也是压强的，一个潜水器械潜入太平洋下11000米a，压强是多少. p=ρgh=1000*9.8*11000=107800000b，如果潜水器的镜子表面的直径是16厘米，问压力，跟第一题一样的，F=ps=ρgh*s=1000*9.8*11000*0.08^2=689920Nc，考减法的，说的是比较第一题和第二题B的压力大小，689920-3939=685981N第三题考浮力的，一个装有碎石的船，宽4米，长1米，当把碎石装在船上时，船下沉了2米，问碎石的重量。G=F浮= ρgV=1000*9.8*4*10*2=784000N
绝代双椒
1.一个4公斤的玩具船浮在水上，密度是水的0.7倍，排出的水的质量是多少？----4公斤 2.一个3公斤的石块悬在水中时，它的显示质量是1.5公斤。石块的密度是水的密度的多少倍？ ----1.5倍3.地球半径的百分之多少等于地球大气的近似高度？（地球的大气延伸到约30公里的高空，地球的半径是6400公里）----0.47
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