A uniform ladder 7.10m long weighing 500N rests wi

问题描述：

A uniform ladder 7.10m long weighing 500N rests with one end on the ground and the other end against a perfectly smooth vertical wall.The ladder rises at 55.0∘ above the horizontal floor.A 800N painter finds that she can climb 2.95m up the ladder,measured along its length,before it begins to slip.
What force does the wall exert on the ladder?
Find the friction force that the floor exerts on the ladder
Find the normal force that the floor exerts on the ladder.

1个回答分类：英语 2014-11-11

问题解答：

我来补答

Sol:
sin(55°) = 0.82;
cos(55°) = 0.57
(1) the force which the wall exert on the ladder is only the normal force.
(2) by the force balance equation.
N = G1 + G2 = 1300N,
by the moment balance equation.
NL = fl + G1l1 + G2l2
where,
L = 7.10m× 0.57 = 4.047m,
l = 7.10m × 0.82 = 5.822m,
l1 = 7.10 ÷ 2 × 0.57 = 2.024m,
l2 = (7.10 - 2.95)m × 0.57 = 2.366m
we'll get
f = 408.85N
再问：第一题的意思是求那个normal force,另第三题的答案是什么？
再答： N1 = G1 = 500N.
第三问在前面，N = 1300N
再问：第一问答案好像不对，应与摩擦力相等，已明白

展开全文阅读

上一页：请给出详细解题过程

下一页：绘图