Stair-climbing car is a kind of small car made by lever principle, which is used to carry heavy objects upstairs. Its structure is shown in figure 1, and q and o' are connected by a shaft. Figure 2 shows the use process of the stair climbing vehicle. Think of the car body as a lever, and in the process of pressing the wheel, the O axis is the fulcrum. Under normal circumstances, the distance between the center of gravity C of the transported heavy object (such as gas tank) and the O axis is very close (that is, the resistance arm is very small), while the handlebar is very long (that is, the power arm is very large), so the required hand pressure F 1 is far less than the weight g of the object. After the wheel climbs a flight of stairs, it should immediately lift the car body to complete a stair climbing action. At this time, the body is still regarded as a lever. Because the fulcrum in this process is the axle A, the power arm is still larger than the resistance arm, and the lifting force F2 required by the hand is also smaller than the weight g ... It can be seen that the stair climbing vehicle is a very labor-saving household lifting and handling tool.