题目

Climate change leads to a threat to the world’s sandy beaches, and as many as half of them could disappear by 2100, a new study has found. Even by 2050 some coastlines could be unrecognizable from what we see today, with 10% to 12% facing severe erosion (侵蚀).Using updated sea level rise predictions, the researchers analyzed how beaches around the world would be in a future with higher seas and more damaging storms. They also considered natural processes like wave erosion, as well as human factors-like coastal building developments, all of which can affect a beach’s health. The study fo质量为m的物体从地面上方H高处无初速度释放,落在地面后出现一个深度为h的坑,如图所示.在不计空气阻力的情况下,对全过程的以下说法中正确的是( )A.外力对物体做的总功为零B.物体的机械能减少mg(H+h)C.地面对物体的阻力对物体做功为﹣mgHD.地面对物体的平均阻力大小为
英语 试题推荐