Forces Make Things Move

Forces Make Things Move

力使物体运动

If you push a toy car, you can make it move across the floor. Your push moves the car. Your push is a force. Forces get things moving. Forces also make things stop. When the toy car rolls across the floor and stops, a force stopped it. Forces also make things speed up or slow down.

如果你推一辆玩具车，你可以使它在地板上移动。 你的一推使汽车移动。你的推动是一种力。 力使物体运动。 力量也能让事情停止。 当玩具车在地板上滚动并停下来时，一股力使它停下来。力也使物体加速或减速。

Any push or pull is a force. Forces can move things farther away or bring them closer. Some forces are very strong. Some are so weak, you can't feel them at all. Nothing starts moving until it is pushed or pulled. If you don't push your toy car, it just sits there--unless something else pushes it, like the wind or your cat or your big brother. The wind, your cat, and your big brother can all produce force. The force moves your car. Any time your car is moving, a force made it start. The heavier an object is, the more force it takes to start it moving. If you want to run across the yard, your feet have to push on the ground to get you moving.

任何推或拉都是一种力。力可以使物体远离，也可以使物体靠近。有些力量非常强大。有些太弱了，你根本感觉不到它们。 在被推或被拉之前，任何东西都不会移动。如果你不推你的玩具车，它就会呆在那里——除非有别的东西推它，比如风、你的猫或你的哥哥。风、你的猫和你的大哥都能产生力。这个力移动你的车。 任何时候你的车在移动，都有一个力使它启动。物体越重，使其运动所需的力就越大。如果你想跑过院子，你的脚必须蹬地才能动起来。

If you and your big brother decide to have a race, his feet will have to push harder on the ground than yours. Why? Because he weighs more. It takes more force to make him move. Once you are running, only another force can stop you. Your feet push on the ground to make you stop. If you want to stop quickly, it takes more force than if you want to stop slowly. You'll have to push harder.

如果你和你哥哥决定比赛，他的脚就得比你的脚蹬地更用力。为什么?因为他更重。要让他动起来需要更大的力量。 一旦你开始奔跑，只有另一种力量能阻止你。你的脚踩在地上让你停下来。如果你想快速停车，比慢速停车需要更大的力量。你得再加把劲。

It takes a lot of force to start heavy things moving. That's why your living room couch doesn't fly across the room when you bump into it. It's why a breeze can't blow your family's car off the driveway. Other things, like leaves and papers and hats, don't weigh very much. Even tiny forces can make them fly around. A little wind makes enough force to make them move.

使重物移动需要很大的力。这就是为什么当你撞到客厅的沙发时，它不会飞过房间的原因。这就是为什么微风不能把你家的车从车道上吹走。其他东西，比如树叶、纸和帽子，都不重。即使很小的力也能使它们飞来飞去。一点风就能产生足够的力量使它们移动。

But if your big brother is lying on the living room couch, you're going to have to push pretty hard to force him off.

但如果你的大哥躺在客厅的沙发上，你就得使劲把他推开。