如图所示，一斜面固定在水平面上，顶端O有一小球，若给小球不同的水平初速度，小球将分别落到斜面上的A、B点、斜面底端的C点和水平面上的D点，运动时间依次为t1、t2、t3、t4，不计空气阻力．则（ ）
A．t1＜t2＜t3＜t4
B．t1＜t2＜t3=t4
C．小球落在A、B点时，速度方向与斜面的夹角相同
D．小球落在A、B点时，速度方向与斜面的夹角不相同
A、根据h=
gt2得，t=1 2
，因为hA＜hB＜hC=hD，则t1＜t2＜t3=t4．故A错误，B正确．2h g
C、因为平抛运动在某时刻速度与水平方向夹角的正切值是位移与水平方向夹角正切值的2倍，落在A、B两点位移与水平方向的夹角相等，等于斜面的倾角，则速度与水平方向的夹角相等，所以速度方向与斜面的夹角相同．故C正确，D错误．
故选：BC．
Rescuers have found the bodies of over 130 people killed in two ferry disasters in Bangladesh．The accidents happened during a storm that hit the country on April 21st．Hundreds more are missing or feared to be dead． The two ferries sank in different rivers near the capital city of Dhakfi as strong winds and rain hit the South Asian country．The government has since banned all ferries and other boats from traveling at night during the April-May stormy season. One of the ferries，MV Mitali，was carrying far more people than it was supposed to．About 400 passengers fitted into a space made for just 300，police said．The second ferry carried about 100 passengers． “The number of deaths is certain to rise．”said an official in charge of the rescue work．“No one really knows how many people were on board the ferry or how many of them survived.” Ferries in Bangladesh don’t always keep passenger lists，making it difficult to determine the exact number of people on board．Besides the ferry accidents，at least 40 people were killed and 400 injured by lightning strikes．falling houses and trees and the sinking of small boats．Storms are common this time of year in Bangladesh，as are boating accidents．Ferry disasters take away hundreds of lives every year in a nation of 130 million people．Officials blame these river accidents on a lack of safety measures, too many passengers in boats and not enough checks on weather conditions． Ferries are a common means of transport in Bangladesh．It is a country covered by about 230 rivers．Some 20,000 ferries use the nation’s Waterways every year．And many of them are dangerously overcrowded．Since 1977, more than 3,000 people have died in some 260 boating accidents． 小题1:The two ferry disasters occurred_______.
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