A 50 kg block of wood is pressed against a smooth wall by a force perpendicular to the wall.If the coefficient of static

A 50 kg block of wood is pressed against a smooth wall by a force perpendicular to the wall.If the coefficient of static friction is 0.13 ,what is the minimum force that is necessary to keep the block of wood in place?
模糊的翻译:
一个50 公斤木块被按没光滑的墙壁由力量垂线对墙壁.如果静态摩擦系数是0.13,以最低到什么的力量来保持木块到位?
At what altitude above the Earth's surface would the gravitational acceleration be 4.9m/s^2 The mass of the Earth is 5.98 x 10^24 kg and radius is 6.37 x 10^6 m
模糊翻译:
在什么高度在地球之上表面重心加速度会是4.9m/s^2?地球的重量是5.98 x 10^24 公斤并且半径是6.37 x 10^6 m.