在动摩擦因数μ=0.2的水平面上有一个质量为m=1kg的小球，小球与水平轻弹簧及与竖直方向成θ=45^o角的不可伸长的轻绳一端相连，如图所示，此时小球处于静止平衡状态，且水平面对小球的弹力恰好为零，当剪断轻绳的瞬间，取g=10m/s²，则：此时轻弹簧的弹力大小____N，小球的加速度大小 ____  m/s²

铝、铁、铜是我们生活中常见的金属。

    My name is Sally Miller. I am a student in No. 3 Middle School. Look! This is a ruler. It's yellow. It's not my ruler. Who lost it?

    “Anna, is this your ruler?” I ask my friend.

    “No, it isn't. My ruler is white. And it's in my pencil box now,” Anna answers.

    “Excuse me, Jack. Is this your ruler?”

    “No, it isn't. My ruler is black.” Jack answers.

    “You can ask your cousin Jenny. She can't find her ruler.”

    “Hi, Jenny! Is this your ruler?” I ask.

    “Yes, it's mine. Thank you very much,” Jenny says. She is very happy to find her ruler.