题目

My husband, Tom, has always been good with animals, but I was still amazed when he befriended a female grouse (松鸡)．It's impossible for a grouse to have any contact (接触) with people．In fact, they're hard to spot,   1   they usually fly off when they hear humans approaching.     This grouse came into our lives in  2  ．Tom was working out in the field when he  3  her walking around at the edge of the field．She was  4  unafraid and seemed to be curious about what he was doing.     Tom saw the   5   bird several times, and she got more comfortable arou一足够高的直立气缸上端开口，用一个厚度不计的活塞封闭了一段高为80 cm的气柱，活塞的横截面积为0. 01 m2，活塞与气缸间的摩擦不计，气缸侧壁通过一个开口与U形管相连，开口离气缸底部的高度为70 cm，开口管内及U形管内的气体体积忽略不计．已知如图所示状态时气体的温度为7 0C , U形管内水银面的高度差h1= 5 cm，大气压强p0 =1. 0 ×105 Pa保持不变，水银的密度=13. 6×103 kg/m3．求： ①活塞的重力． ②现在活塞上添加沙粒，同时对气缸内的气体加热，始终保持活塞的高度不变，此过程缓慢进行，当气体的温度升高到37℃时，U形管内水银面的高度差为多少？ ③若保持第②问中的沙粒质量不变，让气缸内的气体逐渐冷却，那么当气体的温度至少降为多少时，U形管内的水银面变为一样高？