{"id":2499,"date":"2026-05-28T17:15:18","date_gmt":"2026-05-28T11:45:18","guid":{"rendered":"https:\/\/mymockmate.com\/notes\/?p=2499"},"modified":"2026-05-28T17:38:39","modified_gmt":"2026-05-28T12:08:39","slug":"ncert-class-9-science-how-forces-affect-motion-newtons-laws-explained","status":"publish","type":"post","link":"https:\/\/mymockmate.com\/notes\/ncert-class-9-science-how-forces-affect-motion-newtons-laws-explained\/","title":{"rendered":"NCERT Class 9 Science How Forces Affect Motion \u2013 Newton\u2019s Laws Explained"},"content":{"rendered":"<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2499?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\" ><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\" \/><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">1<\/span><\/div>\n<p class=\"wp-block-paragraph\"><strong>Short Intro:<\/strong><br>This chapter explores how forces affect motion, focusing on Newton&#8217;s three laws, friction, and real-world applications. Learn how balanced and unbalanced forces influence objects, and practice step-by-step solutions for various problems.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Quick Information Box:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Chapter:<\/strong> 6 \u2013 How Forces Affect Motion<\/li>\n\n\n\n<li><strong>Class:<\/strong> 9<\/li>\n\n\n\n<li><strong>Key Topics:<\/strong> Force, Friction, Newton&#8217;s Laws of Motion, Acceleration, Mass, Systems of Objects<\/li>\n\n\n\n<li><strong>Unit of Force:<\/strong> Newton (N)<\/li>\n\n\n\n<li><strong>Key Concept:<\/strong> Force produces acceleration and occurs in action-reaction pairs<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Concepts Used (Topics Covered):<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Definition of Force<\/li>\n\n\n\n<li>Measuring Force with Spring Balance<\/li>\n\n\n\n<li>Balanced and Unbalanced Forces<\/li>\n\n\n\n<li>Friction: Static and Kinetic<\/li>\n\n\n\n<li>Newton\u2019s First Law (Law of Inertia)<\/li>\n\n\n\n<li>Newton\u2019s Second Law (F = ma)<\/li>\n\n\n\n<li>Newton\u2019s Third Law (Action-Reaction)<\/li>\n\n\n\n<li>Systems of Objects and Tension Forces<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Important Formulas:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Net Force: <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msub><mi>F<\/mi><mtext>net<\/mtext><\/msub><mo>=<\/mo><mi>m<\/mi><mi>a<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">F_\\text{net} = ma<\/annotation><\/semantics><\/math>Fnet\u200b=ma<\/li>\n\n\n\n<li>Gravitational Force: <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>F<\/mi><mo>=<\/mo><mi>m<\/mi><mi>g<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">F = mg<\/annotation><\/semantics><\/math>F=mg<\/li>\n\n\n\n<li>Acceleration from Kinematics: <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>a<\/mi><mo>=<\/mo><mfrac><mrow><mi>v<\/mi><mo>\u2212<\/mo><mi>u<\/mi><\/mrow><mi>t<\/mi><\/mfrac><\/mrow><annotation encoding=\"application\/x-tex\">a = \\frac{v-u}{t}<\/annotation><\/semantics><\/math><\/li>\n\n\n\n<li>Force from Momentum: <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>F<\/mi><mo>=<\/mo><mfrac><mrow><mi mathvariant=\"normal\">\u0394<\/mi><mi>p<\/mi><\/mrow><mrow><mi mathvariant=\"normal\">\u0394<\/mi><mi>t<\/mi><\/mrow><\/mfrac><\/mrow><annotation encoding=\"application\/x-tex\">F = \\frac{\\Delta p}{\\Delta t}<\/annotation><\/semantics><\/math><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Questions &amp; Step-by-step Solutions:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Net Force on a Block:<\/strong>\n<ul class=\"wp-block-list\">\n<li>Two forces: 10 N and 6 N acting on a block.<\/li>\n\n\n\n<li><strong>Case (a)<\/strong>: Same direction \u2192 <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msub><mi>F<\/mi><mtext>net<\/mtext><\/msub><mo>=<\/mo><mn>10<\/mn><mo>+<\/mo><mn>6<\/mn><mo>=<\/mo><mn>16<\/mn><mtext>\u2009<\/mtext><mi>N<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">F_\\text{net} = 10 + 6 = 16\\,N<\/annotation><\/semantics><\/math> (right)<\/li>\n\n\n\n<li><strong>Case (b)<\/strong>: Opposite direction \u2192 <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msub><mi>F<\/mi><mtext>net<\/mtext><\/msub><mo>=<\/mo><mn>10<\/mn><mo>\u2212<\/mo><mn>6<\/mn><mo>=<\/mo><mn>4<\/mn><mtext>\u2009<\/mtext><mi>N<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">F_\\text{net} = 10 &#8211; 6 = 4\\,N<\/annotation><\/semantics><\/math> (right)<\/li>\n\n\n\n<li><strong>Case (c)<\/strong>: Opposite direction \u2192 <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msub><mi>F<\/mi><mtext>net<\/mtext><\/msub><mo>=<\/mo><mn>10<\/mn><mo>\u2212<\/mo><mn>6<\/mn><mo>=<\/mo><mn>4<\/mn><mtext>\u2009<\/mtext><mi>N<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">F_\\text{net} = 10 &#8211; 6 = 4\\,N<\/annotation><\/semantics><\/math> (left)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Frictional Force:<\/strong>\n<ul class=\"wp-block-list\">\n<li>If applied force &lt; friction \u2192 object stationary<\/li>\n\n\n\n<li>If applied force &gt; friction \u2192 object accelerates<\/li>\n\n\n\n<li>Use <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><msub><mi>F<\/mi><mtext>net<\/mtext><\/msub><mo>=<\/mo><msub><mi>F<\/mi><mtext>applied<\/mtext><\/msub><mo>\u2212<\/mo><msub><mi>F<\/mi><mtext>friction<\/mtext><\/msub><\/mrow><annotation encoding=\"application\/x-tex\">F_\\text{net} = F_\\text{applied} &#8211; F_\\text{friction}<\/annotation><\/semantics><\/math><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Newton\u2019s First Law:<\/strong>\n<ul class=\"wp-block-list\">\n<li>Object moves with constant velocity if net force = 0.<\/li>\n\n\n\n<li>Example: Force on moving box equals friction \u2192 box continues at constant speed<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Newton\u2019s Second Law Problems:<\/strong>\n<ul class=\"wp-block-list\">\n<li>Example: Push a 25 kg block with net force 5 N \u2192 <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>a<\/mi><mo>=<\/mo><mi>F<\/mi><mi mathvariant=\"normal\">\/<\/mi><mi>m<\/mi><mo>=<\/mo><mn>0.2<\/mn><mtext>\u2009<\/mtext><mi>m<\/mi><mi mathvariant=\"normal\">\/<\/mi><msup><mi>s<\/mi><mn>2<\/mn><\/msup><\/mrow><annotation encoding=\"application\/x-tex\">a = F\/m = 0.2\\, m\/s^2<\/annotation><\/semantics><\/math><\/li>\n\n\n\n<li>Displacement in 2 s: <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>s<\/mi><mo>=<\/mo><mi>u<\/mi><mi>t<\/mi><mo>+<\/mo><mn>0.5<\/mn><mi>a<\/mi><msup><mi>t<\/mi><mn>2<\/mn><\/msup><mo>=<\/mo><mn>0<\/mn><mo>+<\/mo><mn>0.5<\/mn><mo>\u2217<\/mo><mn>0.2<\/mn><mo>\u2217<\/mo><mn>4<\/mn><mo>=<\/mo><mn>0.4<\/mn><mtext>\u2009<\/mtext><mi>m<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">s = ut + 0.5at^2 = 0 + 0.5*0.2*4 = 0.4\\, m<\/annotation><\/semantics><\/math><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Sports Car Force Calculation:<\/strong>\n<ul class=\"wp-block-list\">\n<li>Mass 1500 kg, <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>v<\/mi><mo>=<\/mo><mn>0<\/mn><mo>\u2192<\/mo><mn>10<\/mn><mtext>\u2009<\/mtext><mi>m<\/mi><mi mathvariant=\"normal\">\/<\/mi><mi>s<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">v = 0 \\to 10\\, m\/s<\/annotation><\/semantics><\/math> in 5 s \u2192 <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>a<\/mi><mo>=<\/mo><mn>2<\/mn><mtext>\u2009<\/mtext><mi>m<\/mi><mi mathvariant=\"normal\">\/<\/mi><msup><mi>s<\/mi><mn>2<\/mn><\/msup><\/mrow><annotation encoding=\"application\/x-tex\">a = 2\\, m\/s^2<\/annotation><\/semantics><\/math><\/li>\n\n\n\n<li><math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>F<\/mi><mo>=<\/mo><mi>m<\/mi><mi>a<\/mi><mo>=<\/mo><mn>1500<\/mn><mo>\u2217<\/mo><mn>2<\/mn><mo>=<\/mo><mn>3000<\/mn><mtext>\u2009<\/mtext><mi>N<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">F = ma = 1500*2 = 3000\\,N<\/annotation><\/semantics><\/math><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>Newton\u2019s Third Law Applications:<\/strong>\n<ul class=\"wp-block-list\">\n<li>Pushing a table while sitting on a chair \u2192 chair moves backward<\/li>\n\n\n\n<li>Rocket launches: gas expelled downward \u2192 rocket moves upward<\/li>\n\n\n\n<li>Forces equal in magnitude but act on different objects<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>System of Two Boxes:<\/strong>\n<ul class=\"wp-block-list\">\n<li>External force <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>F<\/mi><\/mrow><annotation encoding=\"application\/x-tex\">F<\/annotation><\/semantics><\/math>F on combined mass \u2192 <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>a<\/mi><mo>=<\/mo><mi>F<\/mi><mi mathvariant=\"normal\">\/<\/mi><mo stretchy=\"false\">(<\/mo><msub><mi>m<\/mi><mn>1<\/mn><\/msub><mo>+<\/mo><msub><mi>m<\/mi><mn>2<\/mn><\/msub><mo stretchy=\"false\">)<\/mo><\/mrow><annotation encoding=\"application\/x-tex\">a = F\/(m_1 + m_2)<\/annotation><\/semantics><\/math><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Common Mistakes:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Forgetting friction acts opposite to motion<\/li>\n\n\n\n<li>Confusing balanced vs unbalanced forces<\/li>\n\n\n\n<li>Neglecting mass when calculating acceleration<\/li>\n\n\n\n<li>Misinterpreting action-reaction pairs<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Exam Tips:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Always draw a free-body diagram<\/li>\n\n\n\n<li>Identify all forces before applying Newton\u2019s laws<\/li>\n\n\n\n<li>Check the direction of net force<\/li>\n\n\n\n<li>Use SI units consistently<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Practice MCQs:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Two forces 4 N and 5 N act on block P in opposite directions. Net force? (Answer: 1 N)<\/li>\n\n\n\n<li>A 0.1 kg bullet fired from 5 kg gun \u2192 recoil acceleration of gun? (Answer: <math xmlns=\"http:\/\/www.w3.org\/1998\/Math\/MathML\"><semantics><mrow><mi>a<\/mi><mo>=<\/mo><mi>F<\/mi><mi mathvariant=\"normal\">\/<\/mi><mi>m<\/mi><mo>=<\/mo><mn>0.4<\/mn><mtext>\u2009<\/mtext><mi>m<\/mi><mi mathvariant=\"normal\">\/<\/mi><msup><mi>s<\/mi><mn>2<\/mn><\/msup><\/mrow><annotation encoding=\"application\/x-tex\">a = F\/m = 0.4\\, m\/s^2<\/annotation><\/semantics><\/math><\/li>\n\n\n\n<li>Frictionless surface, net force = 0 \u2192 velocity? (Answer: constant)<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>FAQ Section:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Q:<\/strong> Does a stationary object require a force to remain stationary?<br><strong>A:<\/strong> No, only to overcome friction or initiate motion.<\/li>\n\n\n\n<li><strong>Q:<\/strong> Can acceleration be zero if a force is applied?<br><strong>A:<\/strong> Only if net force = 0.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2499?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\" ><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\" \/><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">1<\/span><\/div>\n    <div class=\"xs_social_share_widget xs_share_url after_content \t\tmain_content  wslu-style-1 wslu-share-box-shaped wslu-fill-colored wslu-none wslu-share-horizontal wslu-theme-font-no wslu-main_content\">\n\n\t\t\n        <ul>\n\t\t\t        <\/ul>\n    <\/div> \n","protected":false},"excerpt":{"rendered":"<p> 1 Short Intro:This chapter explores how forces affect motion, focusing on Newton&#8217;s three laws, friction, and real-world<\/p>\n","protected":false},"author":3,"featured_media":2508,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_surecart_dashboard_logo_width":"180px","_surecart_dashboard_show_logo":true,"_surecart_dashboard_navigation_orders":true,"_surecart_dashboard_navigation_invoices":true,"_surecart_dashboard_navigation_subscriptions":true,"_surecart_dashboard_navigation_downloads":true,"_surecart_dashboard_navigation_billing":true,"_surecart_dashboard_navigation_account":true,"postBodyCss":"","postBodyMargin":[],"postBodyPadding":[],"postBodyBackground":{"backgroundType":"classic","gradient":""},"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[22,4,12],"tags":[1341,1346,1343,1345,1340,1342,1344],"class_list":["post-2499","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cbse","category-class-9","category-science","tag-acceleration","tag-class-9","tag-forces","tag-friction","tag-motion","tag-newtons-laws","tag-physics"],"jetpack_publicize_connections":[],"_links":{"self":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2499","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/comments?post=2499"}],"version-history":[{"count":3,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2499\/revisions"}],"predecessor-version":[{"id":2662,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2499\/revisions\/2662"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media\/2508"}],"wp:attachment":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media?parent=2499"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/categories?post=2499"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/tags?post=2499"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}