高速公路上严禁汽车超载,请你用所学的物理知识解释为什么要限制汽车超载.
答:超载增大了对路面的压力,从而增大了压强,使路面损坏,再就是超载的汽车质量大,惯性大,容易出交通事故.
急性乙型肝炎最早出现异常的血清学标志是()。
A.HBsAg
B.抗-HBs
C.HBeAg
D.抗-HBe
E.抗-HBc
What is used to correct for both induced and permanent magnetism,and consequently must be readjusted with radical changes in latitude().
A.Flinders bar
B.Soft iron spheres
C.Fore-and-aft permanent magnets in their trays
D.Heeling magnet