如果每盒钢笔有10支，总售价100元，那么购买钢笔的总钱数y（元）与所买支数x之间的关系式为____．

    My new Chinese teacher is Miss White. She is funny and kind. Her favourite food is salad because it is fresh and healthy. She can sing English songs and play the guitar. There is a lake in front of her house. Behind the house, there is a mountain. So she often climbs the mountain and plays some sports on the weekend. I like my Chinese teacher.

当汽车紧急刹车时，车上的乘客会向  ____    倒(填“前”或“后”)，这是由于乘客有    ____    。  而被踢出去的足球仍能继续向前运动，这是因为  ____      有惯性。一切   ____     都有惯性，惯性的大小与物体的    ____     有关。