一名质量为60kg训练有素的武警战士(视为质点)在楼顶通过一条长绳由静止开始下滑,到地面最短时间t=2.4s.已知该武警战士落地的速度不能大于v=6m/s,做匀减速直线运动时可以产生的最大加速度大小为a=5m/s2,长绳的下端恰好着地,当地的重力加速度g=10m/s2.求:
(2015.福建莆田)
Enjoy Harvesting
Want to relax yourself?
Want to experience country life?
Come and pick litchi!
Free for a taste.
Price:¥20 per kilo Dates: July 20th-July 28th
Add: Changlin village Tel:277-8688
Fitness Band on sale
Smartwatches without the watch
Monitor speed, time, distance, caloties burned, etc.
Long battery(电池)life (5 days)
¥800 (20% off for students)
Tel:289-6799
Visit Sam Mall for more information.
Ice and Snow Festival
Charming Ice Carving
Amazing World of Ice and Snow
Welcome to Fenghuang Park!
Dates: July 1st -July 25th
¥20 for each adult (half for each student)
Tel:288-6299
Super Pillow(枕头)Fight Party
Pillow Fight, a popular activity among young foreigners, has now come to Putian. It's a creative way to release(释放) pressure and stress.
Place:Putian Stadium
Time:2:30-5:00pm, June 28th
Fee:¥50 (pillow included)
Tel:275-6588
2014年是国家对支援西藏工作20周年,20年来,全国投入援藏资金260亿元,实施了援藏项目7000多个,20年间,西藏经济总量增长了13倍。全国援助西藏( )
①有利于维护平等、团结、互助、和谐的社会主义新型民族关系 ②可以加快西藏地区的经济发展,促进民族团结
③能消除民族差别 实现各民族大融合 ④有利于维护国家长期的稳定和边疆安全
生态系统是指在一定的空间范围内,____与____所形成的统一的整体.
在“探究串联电路中的电流特点”实验中,某同学用电流表分别测出图中A、B、C三处的电流大小,并初步得到它们之间关系的结论.为了进一步探究它们之间的关系,下一步他的操作是( )
人从暗处很快进入明处,瞳孔会扩大.(判断对错)