self mass

例句：

1. 1. The self-mass of the object is 50 kilograms.
   物体的自重是50公斤。
2. 2.The self-mass of the car is 2000 kilograms.
   汽车的自重是2000公斤。
3. 3. The self-mass of the earth is approximately 6.3 billion tons.
   地球的自重大约是63亿公吨。