Liǎng ge qiú xiāngzhuàng yǐhòu, zǒng dòngliàng bǎochí bú biàn.
After two balls collide, their total momentum stays the same.
Tips
usage
动量 is the physics term, as in 动量守恒定律 (the law of conservation of momentum). The everyday 'push' of a moving thing is 冲力, and figurative momentum, as in 'the campaign gained momentum', is 势头.
