1，打钩use Gravity物体会有重力的效果。
| Use Gravity | If enabled, the object is affected by gravity. |
2，Use Gravity不打钩，Is Kinematic打钩则把物体放在什么地方，它就是什么地方。
如果Is Kinematic不钩选，物体如果加了box collider，而物体间的box collider相互碰撞，运行时物体会以相碰后的速度运动。
| Is Kinematic | If enabled, the object will not be driven by the physics engine, and can only be manipulated by its Transform. This is useful for moving platforms or if you want to animate a Rigidbody that has a HingeJoint attached. |
