题目

光滑半圆槽的边缘上固定有一轻质定滑轮，轻绳一端连接小球P，绕过光滑的定滑轮A，另一端系在竖直杆上的B点。现将另一个重物G用光滑轻质挂钩挂在轻绳上AB之间的O点，已知整个装置处于静止状态，将绳的B端向上缓慢移动一小段距离，小球P沿半圆槽上移一小段距离后系统重新平衡，有关力的变化情况，下列说法正确的是（） A . 绳的张力大小不变 B . 绳的张力变大 C . 半圆槽对小球P的弹力变小 D . 半圆槽对小球P的弹力变大Tips on Avoiding Traveling CrowdsIf your chosen destination is a hot tourist spot，you are likely to be bothered by masses of tourists，noise and long line ups at your intended site visits. At this point you might wonder why you ever left home. Here are some tips to avoid the crowds and the frustrations that might otherwise ruin your trip.Book tickets in advance1. Smart travelers can avoid the queue when visiting abroad-the London Eye， Britain's Houses of Parliament，Italy's Vatican Museums，and the Louvre in Paris. You can keep cool with online ticket sales.Sign up for special tours.Often special organizations get after-hours or behind-the-scenes access to famous places. You'll get a guided tour and beat the rush.2.But if large crowds routinely ruin your experience，spending a little extra cash will save your trip.3.For shorter lines，fewer people，and better opportunities to interact and enjoy the attraction，stop by during the week. In many cases，you'll have the place to yourself. Take it one step further，and head to museums，galleries or tourism hot spots after 2 pm.4.Watch the weatherSome travelers often cancel their plans when there are reports of a storm on the approach. 5.By keeping an eye on weather broadcasts，brave souls can often score great last-minute deals or empty attractions.A.Talk to people.B.Visit during the week.C.A note of caution-these tours can be costly.D.Here are several ways to help you have a good trip.E.However，sometimes they're not as bad as they sound.F.Then，visiting school groups will have returned to class.G.Purchase tickets online before you leave home，and skip the crowds and endless lines at your destination.