/* 必修第一册第三章；219封面保持不变。 */
.diagram-elastic-contact-3d{background-image:var(--thumbnail-load,url("/static/model-thumbnails/elastic-contact-3d-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-elastic-contact-3d>*{display:none}
.diagram-force-analysis-trainer{background-image:var(--thumbnail-load,url("/static/model-thumbnails/force-analysis-trainer-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-force-analysis-trainer>*{display:none}
.diagram-hooke-law{background-image:var(--thumbnail-load,url("/static/model-thumbnails/hooke-law-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-hooke-law>*{display:none}
.diagram-sliding-friction-control{background-image:var(--thumbnail-load,url("/static/model-thumbnails/sliding-friction-control-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-sliding-friction-control>*{display:none}
.diagram-static-friction-threshold{background-image:var(--thumbnail-load,url("/static/model-thumbnails/static-friction-threshold-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-static-friction-threshold>*{display:none}
.diagram-friction-direction{background-image:var(--thumbnail-load,url("/static/model-thumbnails/friction-direction-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-friction-direction>*{display:none}
.diagram-force-composition{background-image:var(--thumbnail-load,url("/static/model-thumbnails/force-composition-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-force-composition>*{display:none}
.diagram-force-decomposition{background-image:var(--thumbnail-load,url("/static/model-thumbnails/force-decomposition-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-force-decomposition>*{display:none}
.diagram-double-rope-tension{background-image:var(--thumbnail-load,url("/static/model-thumbnails/double-rope-tension-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-double-rope-tension>*{display:none}
.diagram-three-force-equilibrium{background-image:var(--thumbnail-load,url("/static/model-thumbnails/three-force-equilibrium-ch3.png"))!important;background-size:contain!important;background-position:center!important;background-repeat:no-repeat!important;background-color:#f7f9fb!important}
.diagram-three-force-equilibrium>*{display:none}