题目

Win a trip to the OREGON COAST-Dare to Explore the Pacific Ocean. Build the biggest sand castle on the beach. Search tide pools for sea life. Watch the bright orange sunset over the ocean. Whether you’ve been to the Pacific Ocean before or have only closed your eyes and imagined it, we want to know how you would explore the Oregon Coast if you had the chance to go this summer. JUDGING 1. Clear relationship between the Essay and the Drawing 40% 2. Creativity and skill in design and form of the Drawing 40% 3. Expression of the passion to draw and explore 10% 4. Journalistic quality, tidy natur2．一质量为0.5kg的小物块放在水平地面上的A点，距离A点5m的位置B处是一面墙，如图所示．物块以v0=9m/s的初速度从A点沿AB方向运动，在与墙壁碰撞前瞬间的速度为7m/s，碰后以6m/s的速度反向运动直至静止．g取10m/s2．（1）求物块与地面间的摩擦因数μ；（2）若碰撞时间为0.05s，求碰撞过程中墙面对物块平均作用力的大小F；（3）求物块在反向运动过程中克服摩擦力所做的功W．