题目

Your first home, Laurence Yep wrote in his autobiography,The Lost Garden (1991), will always be the one that you rememberbest. For Yep, whose father and maternal grandparents emigrated from China, that home wasan apartment, and the family grocery store it came with , in anAfrican-American neighborhood of San Francisco. As young people, both he andhis older brother, Thomas, helped out at the store. It was there that youngLaurence taught himself to juggle while unpacking endless cartons of soup cans.And it was there that he learned about patience, hard work, and getting alongwith neighbors.   将质量为m的木块放在倾角为θ的斜面上，木块可沿斜面匀速下滑。现用一沿斜面的力F作用于木块，使之沿斜面向上作匀加速运动，如图所示。求木块的加速度。