是PART A里面的对应题~1.the temperature at which a 0.5-centimerter g

是PART A里面的对应题~
1.the temperature at which a 0.5-centimerter gap between 1.0-meter concrete slab in a side walk will close up completely.
答案是confficient of linear expansion.
这一题,求翻译!
2.used to calculate the speed of a lump of clay that hits and sticks to a block of wood suspended as pendulum,give the high to which the block swings and the masses of the block and the clay.
Conservation of both energy and momentum.
这题我知道是动量守恒,但和能量守恒有啥关系?
第二题是不是因为是非弹性碰撞，所以有能量改变？但我怎么判断是弹性还是非弹性~