如果一个物体在运动，根据牛顿第一定律，它会发生什么？

它会以相同的速度和方向继续运动，直到有外力作用于它。

解释一下，为什么当行驶中的公共汽车突然停止时，乘客会向前倾。

因为乘客的身体由于惯性保持原来的运动状态，而公共汽车停止后，乘客的脚因为摩擦力而停止，但上半身仍然保持向前运动的趋势。

例如，在太空中飞行的宇宙飞船，一旦启动，如果没有外力（如摩擦力或空气阻力）的作用，它会一直以恒定的速度和方向运动。

我可以解释牛顿第一定律，并举例说明其在日常生活中的应用。

1
Newton's first law states that objects at rest stay at rest and objects in motion stay in motion with the same velocity unless acted upon by an unbalanced force.
2
The tendency of objects to resist changes in their state of motion is called inertia, which is why Newton's first law is also known as the law of inertia.
3
When a bus starts moving, passengers fall backward because their inertia causes them to resist the change in motion, and when a bus stops, they fall forward because their inertia causes them to continue moving.