One day Eddie and Hobo looked at the ____. Eddie thought he saw a____but Hobo thought it was a ____. Because Hobo saw one ____. Eddie thought there were many bright ____and it was too____, so it couldn't be a plane.
如图所示,某人用滑轮组匀速提升重为720N的物体的过程中,他对水平地面的压强为5×103Pa,已知滑轮组的机械效率是75%,他双脚与水平地面的接触面积是4×10﹣2m2,求:
①他对绳子的拉力;
②此人所受的重力.