Simple machines make work easier, not less work, says Rick Crosslin, scientist. He joined us today to demonstrate how simple machines work. In our case, Randy was the “load” and Amber was the “effort.
一些您可能无法访问的结果已被隐去。
显示无法访问的结果一些您可能无法访问的结果已被隐去。
显示无法访问的结果