已知向量$\overrightarrow{m}=(\lambda +1,1),\overrightarrow{n}=(\lambda +2,2),$若$(\overrightarrow{m}+\overrightarrow{n})\perp (\overrightarrow{m}-\overrightarrow{n})$，则$\lambda =$   （    ）

古诗词阅读。
                                                                                                          登岳阳楼 

                                                                                                        【唐】杜甫
                                                                    昔闻洞庭水，今上岳阳楼。吴楚东南坼，乾坤日夜浮。
                                                                    亲朋无一字，老病有孤舟。戎马关山北，凭轩涕泗流。

   I like my bike. It brings me a lot of fun. When I was an1boy, my father bought it for me. It is my “horse”. I often go to school2 my bike. I like riding a bike 3 it is very convenient. If I go out by bike, it is 4 to find a place for parking it. Bikes are very cheap, so most people can buy one. There are three people in my family. 5of us has a bike. My parents are teachers in my school. In the morning, Mum, Dad and I each 6 to school. However on a rainy day we walk to school, because the road is bad for riding. I think riding bikes can make us7 . It not only helps us exercise more but also 8 the air clean. The bike is very important in Chinese people’s life. So riding bikes can help you to 9 more about China and the Chinese people. Now people in the world say China is the country of bikes because there are 10 bikes in China. I hope people all round the world like them.

如图所示，用绳AC和BC吊起一重物，绳与竖直方向夹角分别为30°和60°，AC绳能承受的最大拉力为150N，而BC绳能承受的最大拉力为100N，求物体最大重力不能超过多少？