如图所示，将一小石块用力竖直向上抛出，请画出石块离开手后在竖直上升过程中所受力的示意图（不计空气阻力和浮力）．
题目分析：由于石块离开手后在竖直上升过程中不计空气阻力和浮力，所以只受到重力的作用，重力的作用点在重心上，方向竖直向下．
石块在上升过程中（不计空气阻力和浮力）．所以只受到的重力作用，从重心竖直向下画，并标上字母符号G，如图所示：
点评：作力的示意图，要用一条带箭头的线段表示力，线段的长度表示力的大小，箭头表示力的方向，起点或终点表示力的作用点
Section B Directions：Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need.
The first tip Dr. Levine gave was about carrying heavy shopping bags. Smaller bags, she said, are better. “You don’t want to load everything up into one bag and lug it around,” Dr. Levine explained. “You want to __43__ the weight on your body.” She also recommended putting heavier items towards the bottom in those bags and lighter items on top. Also, if you can, make __44__ trips to the car to drop off purchases. Travel can be another pain in the back — from carrying heavy luggage. Again, Dr. Levine __45__ not to pack everything into one bag. Even though it may cost more, she said that packing two smaller bags is safer than packing one heavy one. Also, choose a light-weight bag, so that the only weight you’re carrying is the __46__ inside the suitcase. When __47__ bags from an airport carousel, Dr. Levine suggests standing close to the carousel and bending your knees to lift it up. “You want to avoid that reach-and-lift. It puts a lot of __48__ on your lower back,” she said. When it comes to holiday decorating, people can get __49__. Dr. Levine suggests decorating in pairs, so one person can hand the lights and ornaments to the other person to hang, as to avoid reaching or twisting to get what you need. |