§ 29. Тертя. Сили тертя. Коефіцієнт тертя ковзання. Що я знаю і вмію робити

[Error]

_Oboz_Core_ComponentRenderError 
 TypeError: Cannot read property 'FileUrl' of undefined
    at BookViewer (/app/Obozrevatel.MoyaShkola.WebSite/src/commons/components/bookViewer/bookViewer.js:70:136)
    at JSX.<anonymous> (/app/Obozrevatel.MoyaShkola.WebSite/node_modules/@ObozrevatelCoreWebSite/Commons.Base.component.ssr/index.js:256:30)
    at Generator.next (<anonymous>)
    at /app/Obozrevatel.MoyaShkola.WebSite/node_modules/@ObozrevatelCoreWebSite/Commons.Base.component.ssr/index.js:8:71
    at new Promise (<anonymous>)
    at __awaiter (/app/Obozrevatel.MoyaShkola.WebSite/node_modules/@ObozrevatelCoreWebSite/Commons.Base.component.ssr/index.js:4:12)
    at JSX.createElement (/app/Obozrevatel.MoyaShkola.WebSite/node_modules/@ObozrevatelCoreWebSite/Commons.Base.component.ssr/index.js:169:16)
    at BookPagePage.render (/app/Obozrevatel.MoyaShkola.WebSite/src/commons/pages/bookPage/index.ssr.js:952:72)
    at JSX.<anonymous> (/app/Obozrevatel.MoyaShkola.WebSite/node_modules/@ObozrevatelCoreWebSite/Commons.Base.component.ssr/index.js:230:59)
    at Generator.next (<anonymous>)