{"id":1572,"date":"2026-09-08T08:07:33","date_gmt":"2026-09-08T08:07:33","guid":{"rendered":"https:\/\/maroczain.com\/scolaire.maroczain.com\/?page_id=1572"},"modified":"2026-09-08T08:07:33","modified_gmt":"2026-09-08T08:07:33","slug":"dimensions-unites-ordres-de-grandeur-cpge","status":"publish","type":"page","link":"https:\/\/maroczain.com\/scolaire.maroczain.com\/dimensions-unites-ordres-de-grandeur-cpge\/","title":{"rendered":"Dimensions, unit\u00e9s &amp; ordres de grandeur CPGE"},"content":{"rendered":"\n&#8220;`html\n<div id=\"mza-dimensions-cpge\">\n\n<style>\n#mza-dimensions-cpge,#mza-dimensions-cpge *{box-sizing:border-box}\n#mza-dimensions-cpge{\n --navy:#06172c;--navy2:#0d416d;--gold:#c99a36;--gold2:#efd68c;\n --paper:#f5f6f8;--white:#fff;--text:#18283a;--muted:#687789;--line:#dfe5eb;\n font-family:Arial,Helvetica,sans-serif;background:var(--paper);color:var(--text);overflow:hidden\n}\n#mza-dimensions-cpge a{text-decoration:none;color:inherit}\n#mza-dimensions-cpge 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0;color:#526174;cursor:pointer}\n#mza-dimensions-cpge #dimResult{\n display:none;margin-top:18px;padding:20px;border-radius:14px;background:var(--navy);color:#fff\n}\n#mza-dimensions-cpge .cta{\n text-align:center;padding:50px 24px;border-radius:25px;\n background:linear-gradient(135deg,#06172c,#0d416d);color:#fff\n}\n#mza-dimensions-cpge .cta h2{color:#fff}\n#mza-dimensions-cpge .cta p{max-width:760px;margin:0 auto 22px;color:#cfdae4;line-height:1.7}\n\n@media(max-width:900px){\n #mza-dimensions-cpge .grid,\n #mza-dimensions-cpge .grid3,\n #mza-dimensions-cpge .method{grid-template-columns:1fr}\n}\n<\/style>\n\n<header class=\"hero\">\n<div class=\"wrap\">\n\n<span class=\"badge\">COURS 01 \u2022 PHYSIQUE CPGE<\/span>\n\n<h1>Mesurer.<br>V\u00e9rifier. Estimer.<\/h1>\n\n<p class=\"lead\">\nAvant de r\u00e9soudre un probl\u00e8me physique, il faut ma\u00eetriser les unit\u00e9s,\nles dimensions et les ordres de grandeur. L&#8217;analyse dimensionnelle permet\nde d\u00e9tecter imm\u00e9diatement de nombreuses erreurs et d&#8217;anticiper la forme\nd&#8217;une relation physique.\n<\/p>\n\n<div class=\"actions\">\n<a href=\"#cours\" class=\"btn gold\">\ud83d\udcda COMMENCER<\/a>\n<a href=\"#methode\" class=\"btn glass\">\ud83e\udde0 M\u00c9THODE<\/a>\n<a href=\"#exercices\" class=\"btn glass\">\ud83e\udde9 EXERCICES<\/a>\n<a href=\"#qcm\" class=\"btn glass\">\u2753 QCM<\/a>\n<\/div>\n\n<\/div>\n<\/header>\n\n<section id=\"cours\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">1. GRANDEUR PHYSIQUE<\/span>\n<h2>Un nombre seul ne suffit jamais.<\/h2>\n<\/div>\n\n<div class=\"grid\">\n\n<div class=\"card\">\n<h3>Valeur num\u00e9rique<\/h3>\n<p>\nUne mesure poss\u00e8de une valeur num\u00e9rique.\n<\/p>\n\n<div class=\"formula\">\nv = 25\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Unit\u00e9<\/h3>\n<p>\nLa valeur doit \u00eatre accompagn\u00e9e d&#8217;une unit\u00e9.\n<\/p>\n\n<div class=\"formula\">\nv = 25 m\u00b7s\u207b\u00b9\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Dimension<\/h3>\n<p>\nLa dimension indique la nature physique de la grandeur.\n<\/p>\n\n<div class=\"formula\">\n[v] = L T\u207b\u00b9\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Principe<\/h3>\n<p>\nL&#8217;unit\u00e9 d\u00e9pend du syst\u00e8me choisi, mais la dimension physique ne d\u00e9pend pas du choix d&#8217;unit\u00e9s.\n<\/p>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">2. GRANDEURS FONDAMENTALES<\/span>\n<h2>Les briques du syst\u00e8me international.<\/h2>\n<\/div>\n\n<div class=\"grid3\">\n\n<div class=\"card\">\n<h3>Longueur<\/h3>\n<div class=\"formula\">Dimension : L<br>Unit\u00e9 SI : m\u00e8tre (m)<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Masse<\/h3>\n<div class=\"formula\">Dimension : M<br>Unit\u00e9 SI : kilogramme (kg)<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Temps<\/h3>\n<div class=\"formula\">Dimension : T<br>Unit\u00e9 SI : seconde (s)<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Intensit\u00e9 \u00e9lectrique<\/h3>\n<div class=\"formula\">Dimension : I<br>Unit\u00e9 SI : amp\u00e8re (A)<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Temp\u00e9rature<\/h3>\n<div class=\"formula\">Dimension : \u0398<br>Unit\u00e9 SI : kelvin (K)<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Quantit\u00e9 de mati\u00e8re<\/h3>\n<div class=\"formula\">Dimension : N<br>Unit\u00e9 SI : mole (mol)<\/div>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">3. DIMENSIONS D\u00c9RIV\u00c9ES<\/span>\n<h2>Construire une dimension \u00e0 partir des grandeurs fondamentales.<\/h2>\n<\/div>\n\n<div class=\"grid\">\n\n<div class=\"card\">\n<h3>Vitesse<\/h3>\n\n<div class=\"formula\">\n[v] = L T\u207b\u00b9\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Acc\u00e9l\u00e9ration<\/h3>\n\n<div class=\"formula\">\n[a] = L T\u207b\u00b2\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Force<\/h3>\n\n<div class=\"formula\">\nF = ma\n<\/div>\n\n<div class=\"formula\">\n[F] = M L T\u207b\u00b2\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>\u00c9nergie<\/h3>\n\n<div class=\"formula\">\n[E] = M L\u00b2 T\u207b\u00b2\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Puissance<\/h3>\n\n<div class=\"formula\">\n[P] = M L\u00b2 T\u207b\u00b3\n<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Pression<\/h3>\n\n<div class=\"formula\">\n[p] = M L\u207b\u00b9 T\u207b\u00b2\n<\/div>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section id=\"methode\" class=\"dark\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\" style=\"color:#efd68c\">MZA DIMENSION ENGINE<\/span>\n<h2>Le contr\u00f4le automatique d&#8217;une formule.<\/h2>\n<\/div>\n\n<div class=\"method\">\n<div><b>01<\/b><span>IDENTIFIER<\/span><\/div>\n<div><b>02<\/b><span>REMPLACER<\/span><\/div>\n<div><b>03<\/b><span>SIMPLIFIER<\/span><\/div>\n<div><b>04<\/b><span>COMPARER<\/span><\/div>\n<div><b>05<\/b><span>ESTIMER<\/span><\/div>\n<div><b>06<\/b><span>VALIDER<\/span><\/div>\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">4. HOMOG\u00c9N\u00c9IT\u00c9<\/span>\n<h2>On ne peut additionner que des grandeurs de m\u00eame dimension.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nUne \u00e9quation physique doit \u00eatre homog\u00e8ne :\nles deux membres doivent avoir la m\u00eame dimension.\n<\/p>\n\n<div class=\"formula\">\nx = x\u2080 + v\u2080t + \u00bdat\u00b2\n<\/div>\n\n<p>\nChaque terme doit avoir la dimension d&#8217;une longueur.\n<\/p>\n\n<div class=\"formula\">\n[x\u2080]=L\n<\/div>\n\n<div class=\"formula\">\n[v\u2080t]=(LT\u207b\u00b9)T=L\n<\/div>\n\n<div class=\"formula\">\n[at\u00b2]=(LT\u207b\u00b2)T\u00b2=L\n<\/div>\n\n<\/div>\n\n<div class=\"tip\">\nUne \u00e9quation non homog\u00e8ne est forc\u00e9ment fausse. Une \u00e9quation homog\u00e8ne n&#8217;est pas forc\u00e9ment correcte.\n<\/div>\n\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">5. EXEMPLE CLASSIQUE \u2014 PENDULE<\/span>\n<h2>Retrouver la forme d&#8217;une loi.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<p>\nOn suppose que la p\u00e9riode T d&#8217;un pendule d\u00e9pend uniquement de sa longueur \u2113\net de l&#8217;acc\u00e9l\u00e9ration de la pesanteur g :\n<\/p>\n\n<div class=\"formula\">\nT = C \u2113\u1d45 g\u1d5d\n<\/div>\n\n<p>\no\u00f9 C est une constante sans dimension.\n<\/p>\n\n<div class=\"formula\">\n[T] = [\u2113]\u1d45[g]\u1d5d\n<\/div>\n\n<div class=\"formula\">\nT = L\u1d45 (LT\u207b\u00b2)\u1d5d\n<\/div>\n\n<p>\nL&#8217;analyse des exposants de L et T permet d&#8217;identifier \u03b1 et \u03b2,\nsans r\u00e9soudre l&#8217;\u00e9quation du mouvement.\n<\/p>\n\n<\/div>\n\n<div class=\"tip\">\nL&#8217;analyse dimensionnelle d\u00e9termine la structure de la relation, mais pas la constante num\u00e9rique C.\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">6. GRANDEURS SANS DIMENSION<\/span>\n<h2>Quand le r\u00e9sultat est un nombre pur.<\/h2>\n<\/div>\n\n<div class=\"grid\">\n\n<div class=\"card\">\n<h3>Angle<\/h3>\n<p>\nLe radian est consid\u00e9r\u00e9 comme sans dimension dans l&#8217;analyse dimensionnelle usuelle.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Indice de r\u00e9fraction<\/h3>\n\n<div class=\"formula\">\nn = c\/v\n<\/div>\n\n<p>\nRapport de deux vitesses : sans dimension.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Coefficient de frottement<\/h3>\n<p>\nSouvent sans dimension.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Fonctions math\u00e9matiques<\/h3>\n<p>\nL&#8217;argument de exp, sin, cos, ln doit \u00eatre sans dimension.\n<\/p>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">7. PR\u00c9FIXES SI<\/span>\n<h2>Passer rapidement d&#8217;une \u00e9chelle \u00e0 l&#8217;autre.<\/h2>\n<\/div>\n\n<div class=\"grid3\">\n\n<div class=\"card\">\n<h3>Giga<\/h3>\n<div class=\"formula\">G = 10\u2079<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>M\u00e9ga<\/h3>\n<div class=\"formula\">M = 10\u2076<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Kilo<\/h3>\n<div class=\"formula\">k = 10\u00b3<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Milli<\/h3>\n<div class=\"formula\">m = 10\u207b\u00b3<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Micro<\/h3>\n<div class=\"formula\">\u00b5 = 10\u207b\u2076<\/div>\n<\/div>\n\n<div class=\"card\">\n<h3>Nano<\/h3>\n<div class=\"formula\">n = 10\u207b\u2079<\/div>\n<\/div>\n\n<\/div>\n\n<div class=\"tip\">\nAttention aux surfaces et volumes : 1 cm\u00b2 = 10\u207b\u2074 m\u00b2 et 1 cm\u00b3 = 10\u207b\u2076 m\u00b3.\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">8. ORDRES DE GRANDEUR<\/span>\n<h2>Estimer avant de calculer pr\u00e9cis\u00e9ment.<\/h2>\n<\/div>\n\n<div class=\"grid\">\n\n<div class=\"card\">\n<h3>Principe<\/h3>\n<p>\nL&#8217;ordre de grandeur correspond \u00e0 la puissance de dix permettant de situer une valeur.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Exemple<\/h3>\n\n<div class=\"formula\">\nR<sub>Terre<\/sub> \u2248 6,4 \u00d7 10\u2076 m\n<\/div>\n\n<p>\nL&#8217;\u00e9chelle caract\u00e9ristique est de l&#8217;ordre du million de m\u00e8tres.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Pourquoi ?<\/h3>\n<p>\nUn r\u00e9sultat de 10\u00b9\u00b2 m pour le rayon d&#8217;une voiture peut \u00eatre rejet\u00e9 sans refaire tout le calcul.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>R\u00e9flexe concours<\/h3>\n<p>\nToujours confronter un r\u00e9sultat num\u00e9rique \u00e0 une valeur physiquement plausible.\n<\/p>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">9. ESTIMATIONS DE FERMI<\/span>\n<h2>R\u00e9soudre sans disposer de toutes les donn\u00e9es.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<h3>Exemple de mission<\/h3>\n\n<p>\nEstimer le nombre de battements cardiaques d&#8217;une personne pendant une ann\u00e9e.\n<\/p>\n\n<p>\nOn peut prendre un ordre de grandeur raisonnable pour la fr\u00e9quence cardiaque,\npuis estimer le nombre de minutes dans une ann\u00e9e.\n<\/p>\n\n<div class=\"formula\">\nNombre \u2248 fr\u00e9quence \u00d7 dur\u00e9e\n<\/div>\n\n<p>\nL&#8217;objectif n&#8217;est pas une pr\u00e9cision parfaite, mais un r\u00e9sultat coh\u00e9rent \u00e0 l&#8217;\u00e9chelle correcte.\n<\/p>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">10. INCERTITUDE &#038; CHIFFRES SIGNIFICATIFS<\/span>\n<h2>Ne pas afficher une pr\u00e9cision qui n&#8217;existe pas.<\/h2>\n<\/div>\n\n<div class=\"grid\">\n\n<div class=\"card\">\n<h3>Mesure<\/h3>\n\n<div class=\"formula\">\nL = 12,4 \u00b1 0,1 cm\n<\/div>\n\n<p>\nLa mesure n&#8217;est pas connue avec une pr\u00e9cision infinie.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Chiffres significatifs<\/h3>\n<p>\nLe r\u00e9sultat final doit rester coh\u00e9rent avec la pr\u00e9cision des donn\u00e9es.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>Mauvais r\u00e9sultat<\/h3>\n\n<div class=\"formula\">\nv = 13,847263 m\u00b7s\u207b\u00b9\n<\/div>\n\n<p>\nsi les donn\u00e9es n&#8217;ont que deux ou trois chiffres significatifs.\n<\/p>\n<\/div>\n\n<div class=\"card\">\n<h3>R\u00e9flexe<\/h3>\n<p>\nCalculer avec suffisamment de pr\u00e9cision, puis arrondir seulement le r\u00e9sultat final.\n<\/p>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section id=\"exercices\" style=\"background:#efede7\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">11. EXERCICES PROGRESSIFS<\/span>\n<h2>Contr\u00f4ler avant de r\u00e9soudre.<\/h2>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU 1<\/span>\n\n<h3>Exercice 1 \u2014 Dimension d&#8217;une \u00e9nergie<\/h3>\n\n<p>\n\u00c0 partir de l&#8217;expression :\n<\/p>\n\n<div class=\"formula\">\nE<sub>c<\/sub> = \u00bdmv\u00b2\n<\/div>\n\n<p>\nretrouver la dimension de l&#8217;\u00e9nergie cin\u00e9tique.\n<\/p>\n\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaDimHint('dimHint1')\">\ud83d\udca1 INDICE<\/button>\n\n<div id=\"dimHint1\" class=\"hint\">\nRemplacez [m] par M et [v] par LT\u207b\u00b9.\n<\/div>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU 2<\/span>\n\n<h3>Exercice 2 \u2014 Homog\u00e9n\u00e9it\u00e9<\/h3>\n\n<p>\nTester l&#8217;homog\u00e9n\u00e9it\u00e9 de :\n<\/p>\n\n<div class=\"formula\">\nv = v\u2080 + at\u00b2\n<\/div>\n\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaDimHint('dimHint2')\">\ud83d\udca1 INDICE<\/button>\n\n<div id=\"dimHint2\" class=\"hint\">\nComparez la dimension de v avec celle de at\u00b2.\n<\/div>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU 3<\/span>\n\n<h3>Exercice 3 \u2014 Constante gravitationnelle<\/h3>\n\n<p>\nLa loi de Newton s&#8217;\u00e9crit :\n<\/p>\n\n<div class=\"formula\">\nF = G m\u2081m\u2082 \/ r\u00b2\n<\/div>\n\n<p>\nD\u00e9terminer la dimension de G.\n<\/p>\n\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaDimHint('dimHint3')\">\ud83d\udca1 INDICE<\/button>\n\n<div id=\"dimHint3\" class=\"hint\">\nIsolez G puis remplacez les dimensions de F, r et m.\n<\/div>\n<\/div>\n\n<div class=\"exercise\">\n<span class=\"level\">NIVEAU PR\u00c9PA<\/span>\n\n<h3>Exercice 4 \u2014 Temps caract\u00e9ristique<\/h3>\n\n<p>\nOn cherche un temps caract\u00e9ristique \u03c4 construit \u00e0 partir d&#8217;une masse m\net d&#8217;un coefficient de frottement k sachant que :\n<\/p>\n\n<div class=\"formula\">\nF = -kv\n<\/div>\n\n<p>\nRetrouver la d\u00e9pendance de \u03c4 en m et k.\n<\/p>\n\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaDimHint('dimHint4')\">\ud83d\udca1 INDICE<\/button>\n\n<div id=\"dimHint4\" class=\"hint\">\nCommencez par d\u00e9terminer la dimension de k \u00e0 partir de F=kv.\n<\/div>\n<\/div>\n\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">12. PROBLEM LAB<\/span>\n<h2>Mission : retrouver une loi par analyse dimensionnelle.<\/h2>\n<\/div>\n\n<div class=\"card\">\n\n<h3>Chute d&#8217;une goutte<\/h3>\n\n<p>\nOn suppose qu&#8217;une vitesse caract\u00e9ristique v d\u00e9pend :\n<\/p>\n\n<ul>\n<li>d&#8217;une longueur R ;<\/li>\n<li>d&#8217;une masse volumique \u03c1 ;<\/li>\n<li>d&#8217;une acc\u00e9l\u00e9ration g.<\/li>\n<\/ul>\n\n<p>\nOn cherche une relation :\n<\/p>\n\n<div class=\"formula\">\nv = C R\u1d45 \u03c1\u1d5d g\u1d5e\n<\/div>\n\n<p>Votre mission :<\/p>\n\n<ol>\n<li>\u00e9crire les dimensions de v, R, \u03c1 et g ;<\/li>\n<li>construire l&#8217;\u00e9quation dimensionnelle ;<\/li>\n<li>identifier les \u00e9quations sur \u03b1, \u03b2 et \u03b3 ;<\/li>\n<li>v\u00e9rifier si les donn\u00e9es suffisent pour d\u00e9terminer tous les exposants ;<\/li>\n<li>expliquer ce que r\u00e9v\u00e8le une \u00e9ventuelle ind\u00e9termination ;<\/li>\n<li>identifier quel autre param\u00e8tre physique pourrait manquer au mod\u00e8le.<\/li>\n<\/ol>\n\n<div class=\"actions\">\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaDimHint('dimMission1')\">\ud83d\udca1 INDICE<\/button>\n<button type=\"button\" class=\"btn\" style=\"background:#06172c;color:#fff\" onclick=\"mzaDimHint('dimMission2')\">\ud83e\udde0 M\u00c9THODE<\/button>\n<\/div>\n\n<div id=\"dimMission1\" class=\"hint\">\nLa masse volumique a pour dimension M L\u207b\u00b3.\n<\/div>\n\n<div id=\"dimMission2\" class=\"hint\">\nUne analyse dimensionnelle peut r\u00e9v\u00e9ler qu&#8217;un mod\u00e8le est incomplet : si les exposants ne peuvent pas \u00eatre d\u00e9termin\u00e9s de fa\u00e7on unique, cherchez une grandeur physique suppl\u00e9mentaire.\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section class=\"dark\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\" style=\"color:#efd68c\">MZA PHYSICAL CHECK<\/span>\n<h2>Avant de valider un r\u00e9sultat.<\/h2>\n<\/div>\n\n<div class=\"method\">\n<div><b>A<\/b><span>UNIT\u00c9 SI<\/span><\/div>\n<div><b>B<\/b><span>DIMENSION<\/span><\/div>\n<div><b>C<\/b><span>HOMOG\u00c9N\u00c9IT\u00c9<\/span><\/div>\n<div><b>D<\/b><span>SIGNE<\/span><\/div>\n<div><b>E<\/b><span>ORDRE DE GRANDEUR<\/span><\/div>\n<div><b>F<\/b><span>SENS PHYSIQUE<\/span><\/div>\n<\/div>\n\n<\/div>\n<\/section>\n\n<section id=\"qcm\">\n<div class=\"wrap\">\n\n<div class=\"head\">\n<span class=\"kicker\">13. QCM DE VALIDATION<\/span>\n<h2>Diagnostic Dimensions &#038; Unit\u00e9s.<\/h2>\n\n<p>Le score est affich\u00e9 sans r\u00e9v\u00e9ler les r\u00e9ponses correctes.<\/p>\n<\/div>\n\n<div class=\"qcm\">\n\n<form id=\"dimQuiz\">\n\n<div class=\"question\">\n<strong>1. La dimension d&#8217;une vitesse est :<\/strong>\n<label><input type=\"radio\" name=\"d1\" value=\"1\"> LT\u207b\u00b9<\/label>\n<label><input type=\"radio\" name=\"d1\" value=\"0\"> LT<\/label>\n<label><input type=\"radio\" name=\"d1\" value=\"0\"> MT\u207b\u00b9<\/label>\n<label><input type=\"radio\" name=\"d1\" value=\"0\"> L\u00b2T\u207b\u00b9<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>2. La dimension d&#8217;une force est :<\/strong>\n<label><input type=\"radio\" name=\"d2\" value=\"1\"> MLT\u207b\u00b2<\/label>\n<label><input type=\"radio\" name=\"d2\" value=\"0\"> ML\u00b2T\u207b\u00b2<\/label>\n<label><input type=\"radio\" name=\"d2\" value=\"0\"> MT\u207b\u00b9<\/label>\n<label><input type=\"radio\" name=\"d2\" value=\"0\"> LT\u207b\u00b2<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>3. Une \u00e9quation physique non homog\u00e8ne est :<\/strong>\n<label><input type=\"radio\" name=\"d3\" value=\"1\"> n\u00e9cessairement fausse<\/label>\n<label><input type=\"radio\" name=\"d3\" value=\"0\"> toujours correcte<\/label>\n<label><input type=\"radio\" name=\"d3\" value=\"0\"> correcte si les valeurs num\u00e9riques sont petites<\/label>\n<label><input type=\"radio\" name=\"d3\" value=\"0\"> correcte si elle contient une constante<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>4. La dimension d&#8217;une \u00e9nergie est :<\/strong>\n<label><input type=\"radio\" name=\"d4\" value=\"1\"> ML\u00b2T\u207b\u00b2<\/label>\n<label><input type=\"radio\" name=\"d4\" value=\"0\"> MLT\u207b\u00b2<\/label>\n<label><input type=\"radio\" name=\"d4\" value=\"0\"> ML\u207b\u00b9T\u207b\u00b2<\/label>\n<label><input type=\"radio\" name=\"d4\" value=\"0\"> LT\u207b\u00b9<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>5. Dans exp(x), l&#8217;argument x doit \u00eatre :<\/strong>\n<label><input type=\"radio\" name=\"d5\" value=\"1\"> sans dimension<\/label>\n<label><input type=\"radio\" name=\"d5\" value=\"0\"> une longueur<\/label>\n<label><input type=\"radio\" name=\"d5\" value=\"0\"> une masse<\/label>\n<label><input type=\"radio\" name=\"d5\" value=\"0\"> obligatoirement un temps<\/label>\n<\/div>\n\n<div class=\"question\">\n<strong>6. Un ordre de grandeur sert principalement \u00e0 :<\/strong>\n<label><input type=\"radio\" name=\"d6\" value=\"1\"> v\u00e9rifier la plausibilit\u00e9 d&#8217;un r\u00e9sultat<\/label>\n<label><input type=\"radio\" name=\"d6\" value=\"0\"> remplacer syst\u00e9matiquement les calculs exacts<\/label>\n<label><input type=\"radio\" name=\"d6\" value=\"0\"> supprimer les unit\u00e9s<\/label>\n<label><input type=\"radio\" name=\"d6\" value=\"0\"> obtenir toujours dix chiffres significatifs<\/label>\n<\/div>\n\n<button type=\"button\" class=\"btn gold\" onclick=\"mzaDimScore()\">\nVALIDER MON QCM\n<\/button>\n\n<\/form>\n\n<div id=\"dimResult\"><\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<section>\n<div class=\"wrap\">\n\n<div class=\"cta\">\n\n<div style=\"font-size:43px\">[F] = MLT\u207b\u00b2<\/div>\n\n<h2>Une formule doit d&#8217;abord survivre au contr\u00f4le physique.<\/h2>\n\n<p>\nDimensions, unit\u00e9s, homog\u00e9n\u00e9it\u00e9 et ordres de grandeur constituent\nle premier filtre de tout raisonnement physique s\u00e9rieux.\nCe r\u00e9flexe fera gagner du temps dans pratiquement tous les chapitres suivants.\n<\/p>\n\n<div class=\"actions\" style=\"justify-content:center\">\n<a href=\"#cours\" class=\"btn gold\">\ud83d\udcda REVOIR LE COURS<\/a>\n<a href=\"#exercices\" class=\"btn glass\">\ud83e\udde9 EXERCICES<\/a>\n<a href=\"#qcm\" class=\"btn glass\">\u2753 REFAIRE LE QCM<\/a>\n<\/div>\n\n<\/div>\n<\/div>\n<\/section>\n\n<script>\nfunction mzaDimHint(id){\n const el=document.getElementById(id);\n if(!el)return;\n el.style.display = el.style.display===\"block\" ? \"none\" : \"block\";\n}\n\nfunction mzaDimScore(){\n const form=document.getElementById(\"dimQuiz\");\n const result=document.getElementById(\"dimResult\");\n\n let score=0;\n let complete=true;\n\n [\"d1\",\"d2\",\"d3\",\"d4\",\"d5\",\"d6\"].forEach(function(name){\n   const answer=form.querySelector('input[name=\"'+name+'\"]:checked');\n\n   if(!answer){\n     complete=false;\n   }else{\n     score+=Number(answer.value);\n   }\n });\n\n result.style.display=\"block\";\n\n if(!complete){\n   result.innerHTML=\"<strong>R\u00e9pondez aux 6 questions avant de valider.<\/strong>\";\n   return;\n }\n\n const pct=Math.round(score\/6*100);\n\n let level=\"Dimensions et unit\u00e9s \u00e0 consolider\";\n if(pct>=50) level=\"Fondations acquises\";\n if(pct>=67) level=\"Bon niveau\";\n if(pct>=84) level=\"Tr\u00e8s bonne ma\u00eetrise\";\n if(pct===100) level=\"Excellent r\u00e9flexe CPGE\";\n\n result.innerHTML=\n \"<strong style='font-size:30px;color:#efd68c'>\"+pct+\"%<\/strong>\"+\n \"<p><b>\"+level+\"<\/b><\/p>\"+\n \"<p>Score : \"+score+\" \/ 6<\/p>\"+\n \"<p>Les r\u00e9ponses correctes et la correction d\u00e9taill\u00e9e restent masqu\u00e9es.<\/p>\";\n}\n<\/script>\n\n<\/div>\n&#8220;`\n","protected":false},"excerpt":{"rendered":"<p>&#8220;`html COURS 01 \u2022 PHYSIQUE CPGE Mesurer.V\u00e9rifier. Estimer. Avant de r\u00e9soudre un probl\u00e8me physique, il faut ma\u00eetriser les unit\u00e9s, les dimensions et les ordres de grandeur. L&#8217;analyse dimensionnelle permet de d\u00e9tecter imm\u00e9diatement de nombreuses erreurs et d&#8217;anticiper la forme d&#8217;une relation physique. \ud83d\udcda COMMENCER \ud83e\udde0 M\u00c9THODE \ud83e\udde9 EXERCICES \u2753 QCM 1. GRANDEUR PHYSIQUE Un nombre [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-1572","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages\/1572","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/comments?post=1572"}],"version-history":[{"count":1,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages\/1572\/revisions"}],"predecessor-version":[{"id":1574,"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/pages\/1572\/revisions\/1574"}],"wp:attachment":[{"href":"https:\/\/maroczain.com\/scolaire.maroczain.com\/wp-json\/wp\/v2\/media?parent=1572"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}