在烂泥地面行走时，两脚会深深地陷下去．如果肩上再扛着个重物，两脚陷得就更深了，如果在烂泥地上垫一块木板，人站在上面，下陷就浅的多．加了木板，重物、人和木板的总重力增大了，怎么反而陷得浅了呢？这是由于在这两种情况下，重力分布在面积不同的烂泥地面的缘故．同样 When walking on the muddy ground, both feet will sink deeply. If there is a heavy object on the shoulder, the two feet will sink deeper. If a wooden plank is placed on the mud, people stand on it and the sinking will be much lighter. With the addition of planks, the total weight of the weights, people, and planks has increased. How can it be lightened? This is due to the fact that in both cases, gravity is distributed over differently-sized sludge floors. same