题目内容：

Fill in the blanks with proper words （在短文的空格内填入适当的词，使其内容通顺，每空格限填一词，首字母已给）

You move every day. Every time you sit down, walk, ride a bike, or eat your food, you are moving. You e1. move while you are sitting in a chair. What gets you moving, keeps you moving, and helps you to move the way you want to move?

One force that helps you move is gravity. Gravity pulls you toward Earth. Why? Earth is bigger and h2. than you are, so you’re pulled by Earth’s gravity. How does that help you? When you take a step, gravity pulls on your foot. That pulling helps you put your foot down. Then, you can move your o3. foot. Do you like to play baseball? Gravity makes the baseball fall after it is h4.. Then, as gravity pulls the ball toward the ground, and can catch the ball.

Friction also helps you move. Friction happens when two o5. rub against each other. How does friction help you move? When you walk, friction keeps your feet from slipping. When you hold a pencil, friction helps keep it in your h6.. and friction makes the brakes on your bike work. too.

Inertia also helps you. Inertia is a sort of rule: it tells us two things; Things that are in movement will remain in movement until something stops them; and things that are at rest will stay at rest unless something moves them. When you ride your bike, it will keep going until you stop it, and when you sit down to read, you will stay where you are until you are r7. to move.

Next time you move, think about gravity, friction and inertia. All of them help to get you where you want to go.

① gravity n. 重力    ② friction  n. 摩擦力  ③ inertia n. 惯性