题干

在“探究求合力的方法”的实验中,需要将橡皮条的一端固定在水平木板上,另一端系上两根细绳,细绳的另一端都有绳套(如图).实验中需用两个弹簧测力计分别勾住绳套,并互成角度地拉橡皮条,使橡皮条伸长,结点到达某一位置O.

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同类题3

阅读下列短文,从每题所给的ABC和D四个选项中,选出最佳选项。

A

Washington, D.C. Bicycle Tours

Cherry Blossom Bike Tour in Washington, D.C

    Duration: 3 hours

    This small group bike tour is a fantastic way to see the world-famous cherry trees with beautiful flowers of Washington, D.C. Your guide will provide a history lesson about the trees and the famous monuments where they blossom. Reserve your spot before availability - and the cherry blossoms - disappear!

Washington Capital Monuments Bicycle Tour

    Duration: 3 hours (4 miles)

    Join a guided bike tour and view some of the most popular monuments in Washington, D.C. Explore the monuments and memorials on the National Mall as your guide shares unique

facts and history at each stop. Guided tour includes bike, helmet, cookies and bottled water.

Capital City Bike Tour in Washington, D.C.

    Duration: 3 hour

    Morning or Afternoon this bike tour is the perfect tour for D.C. newcomers and locals looking to experience Washington, D.C.in a healthy way with minimum effort. Knowledge guides will entertain you with the most interesting stories about Presidents. Congress, memories, and parks. Comfortable bikes and a smooth tour route(路线) make cycling between the sites fun and relaxing.

Washington Capital Sites at Night Bicycle Tour

    Duration: 3 hour (7 miles)

    Join a small group hike tour for an evening of exploration in the heart of Washington, D.C. Get up close to the monuments and memorials as you bike the sites of Capitol Hill and the National Mall. Frequent stops are made for photo taking as your guide offers unique facts and history. Tour includes bike, helmet, and bottled water. All rides are equipped with reflective vests and safety lights.