motion in a straight line

• 直线运动

motion in a straight line的用法和样例：

例句

1. The tendency of a body in motion to continue in motion along a straight line is known as inertia.
   运动物体继续作直线运动的倾向叫惯性。
2. A little known theory of Kepler's held that comets were celestial bodies moving along straight lines.
   另一个鲜为人们所知的开普勒理论认为，彗星是沿直线运动的天体。