■解答
① \(mg\cos\theta\) ② \(kl-mg\sin\theta\) ③ \(\displaystyle\frac{mg}{k}(\sin\theta+\mu \cos\theta)\)
④ \(-\mu'mg\cos\theta\) ⑤ \(mg(l_1+l_2)\sin\theta\) ⑥ \(\displaystyle\frac{k}{2}(l_2^2-l_1^2)\)
⑦ \(\displaystyle\frac{2mg}{k}(\mu'\cos\theta+\sin\theta)\) ⑧ \(kl_2+mg\sin\theta\) ⑨ \(\displaystyle\frac{2\mu' mg}{k}\cos\theta\)
⑩ \(\displaystyle\frac{mg}{k}(\sin\theta-\mu'\cos\theta)\) ⑪ \(\sqrt{\displaystyle\frac{k}{m}}(l_2+l_3)\)
