欧美精品在欧美一区二区少妇,久久久久成人影视,99热在线精品呀,草莓视频手机在线观看

What Is the Force of Gravity?

If you throw a ball up, it will come down again. What makes it come down? The ball comes down because it is pulled or attracted towards the Earth. The Earth exerts a force of attraction on all objects. Objects that are nearer to the Earth are attracted to it with a greater force than those that are further away. This force of attraction is known as the force of gravity. The gravitational force acting on an object at the Earth’s surface is called the weight of the object.

All the heavenly bodies in space like the moon, the planets and the stars also exert an attractive force on objects. The bigger and heavier a body is, the greater is its force of gravity. Thus, since the moon is a smaller body than Earth, the force it exerts on an object at its surface is less than that exerted by the Earth on the same object on the Earth’s surface. In fact, the moon’s gravitational force is only one-sixth that of the Earth. This means that an object weighing 120 kilograms on Earth will only weigh 20 kilograms on the moon. Therefore on the moon you could lift weights which are six times heavier than the heaviest weight that you can lift on Earth.

The Earth’s gravitational force or pull keeps us and everything else on Earth from floating away to space. To get out into space and travel to the moon or other planets we have to overcome the Earth’s gravitational pull.

相關(guān)內(nèi)容：

2013年9月翻譯資格考試每日一練匯總

（責(zé)任編輯：中大編輯）

共2頁(yè),當(dāng)前第1頁(yè)  第一頁(yè)  前一頁(yè)  下一頁(yè)