{"id":2510,"date":"2026-05-28T17:14:46","date_gmt":"2026-05-28T11:44:46","guid":{"rendered":"https:\/\/mymockmate.com\/notes\/?p=2510"},"modified":"2026-05-28T17:14:49","modified_gmt":"2026-05-28T11:44:49","slug":"ncert-class-9-science-work-energy-and-simple-machines-class-9-solutions","status":"publish","type":"post","link":"https:\/\/mymockmate.com\/notes\/ncert-class-9-science-work-energy-and-simple-machines-class-9-solutions\/","title":{"rendered":"NCERT Class 9 Science Work, Energy and Simple Machines Class 9 Solutions"},"content":{"rendered":"<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2510?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\"><\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Short Intro<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">This chapter explains the concepts of work, energy, power, and simple machines with practical examples and numerical problems. Students will learn how forces perform work, how energy changes from one form to another, and how machines make our work easier.<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Quick Information Box<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Topic<\/th><th>Details<\/th><\/tr><\/thead><tbody><tr><td>Chapter Name<\/td><td>Work, Energy and Simple Machines<\/td><\/tr><tr><td>Class<\/td><td>Grade 9<\/td><\/tr><tr><td>Subject<\/td><td>Science \/ Physics<\/td><\/tr><tr><td>Important Topics<\/td><td>Work, Energy, Power, Kinetic Energy, Potential Energy, Machines<\/td><\/tr><tr><td>SI Unit of Work<\/td><td>Joule (J)<\/td><\/tr><tr><td>SI Unit of Power<\/td><td>Watt (W)<\/td><\/tr><tr><td>Key Formula<\/td><td>W = F \u00d7 s<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h1 class=\"wp-block-heading\">Concepts Used (Topics Covered)<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Work Done by Force<\/li>\n\n\n\n<li>Positive and Negative Work<\/li>\n\n\n\n<li>Work-Energy Theorem<\/li>\n\n\n\n<li>Forms of Energy<\/li>\n\n\n\n<li>Kinetic Energy<\/li>\n\n\n\n<li>Potential Energy<\/li>\n\n\n\n<li>Conservation of Mechanical Energy<\/li>\n\n\n\n<li>Power<\/li>\n\n\n\n<li>Pulley<\/li>\n\n\n\n<li>Inclined Plane<\/li>\n\n\n\n<li>Lever and Mechanical Advantage<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Important Formulas<\/h1>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Work Done<br>W = F \u00d7 s<\/li>\n\n\n\n<li>Kinetic Energy<br>KE = \u00bd mv\u00b2<\/li>\n\n\n\n<li>Potential Energy<br>PE = mgh<\/li>\n\n\n\n<li>Power<br>P = W \/ t<\/li>\n\n\n\n<li>Mechanical Advantage<br>MA = Load \/ Effort<\/li>\n\n\n\n<li>Inclined Plane<br>MA = Length \/ Height<\/li>\n\n\n\n<li>Lever Principle<br>Effort \u00d7 Effort Arm = Load \u00d7 Load Arm<\/li>\n<\/ol>\n\n\n\n<h1 class=\"wp-block-heading\">Questions &amp; Step-by-step Solutions with Explanation<\/h1>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">Q1. State whether True or False.<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Work is said to be done when a force is applied, even if the object does not move.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Work is done only when displacement occurs.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If displacement = 0, then work done = 0.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">False<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Lifting a bucket vertically upward results in positive work done on the bucket.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Force and displacement are in the same direction.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore, work done is positive.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">True<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) The SI unit for both work and energy is joule (J).<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Both work and energy are measured in joules.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">True<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iv) A motionless stretched rubber band has kinetic energy.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The rubber band is not moving, so it has no kinetic energy.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It stores potential energy.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">False<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(v) Energy can change from one form to another.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electrical energy changes into light and heat energy in a bulb.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">True<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q2. Fill in the blanks.<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Work done = ______ \u00d7 ______<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Force \u00d7 Displacement<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) 1 joule of work is done when a force of ______ newton displaces an object by 1 metre.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">1 newton<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) Expression for kinetic energy is ______<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">\u00bd mv\u00b2<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iv) Potential energy of an object is ______<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">mgh<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(v) Power is defined as the ______ at which work is done.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Rate<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q3. Ball Reaches Highest Point<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Correct Statements:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Kinetic energy is zero<\/li>\n\n\n\n<li>Potential energy is maximum<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">At the highest point velocity becomes zero, therefore kinetic energy becomes zero.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q4. Energy Transformations<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Situation<\/th><th>Energy Conversion<\/th><\/tr><\/thead><tbody><tr><td>Truck moving uphill<\/td><td>Kinetic \u2192 Potential<\/td><\/tr><tr><td>Watch spring unwinding<\/td><td>Potential \u2192 Kinetic<\/td><\/tr><tr><td>Photosynthesis<\/td><td>Light \u2192 Chemical<\/td><\/tr><tr><td>Water flowing from dam<\/td><td>Potential \u2192 Kinetic<\/td><\/tr><tr><td>Burning matchstick<\/td><td>Chemical \u2192 Heat and Light<\/td><\/tr><tr><td>Firecracker explosion<\/td><td>Chemical \u2192 Sound, Light, Heat<\/td><\/tr><tr><td>Microphone<\/td><td>Sound \u2192 Electrical<\/td><\/tr><tr><td>Electric bulb<\/td><td>Electrical \u2192 Light<\/td><\/tr><tr><td>Solar panel<\/td><td>Light \u2192 Electrical<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q5. Student Lifted to Top Floor<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Given:<br>m = 50 kg<br>h = 72.5 m<br>g = 10 m\/s\u00b2<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Formula:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">PE = mgh<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Calculation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">PE = 50 \u00d7 10 \u00d7 72.5<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">PE = 36250 J<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">(i) Gain in PE = 36250 J<br>(ii) Gain in PE while climbing stairs = 36250 J<br>(iii) Potential energy depends only on height, not on path.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q6. Crane Lifting Mass<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Potential energy depends on height.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">20th floor height is double of 10th floor.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Therefore:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Energy required becomes double.<\/li>\n\n\n\n<li>Time also becomes double.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Power = Work \/ Time<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Hence power remains same.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Energy required = Double<\/li>\n\n\n\n<li>Power required = Same<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q7. Factors Affecting Energy in Raising Flag<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Energy depends on:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Mass of flag<\/li>\n\n\n\n<li>Height of pole<\/li>\n\n\n\n<li>Gravitational acceleration<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Raising slowly or quickly does not change work done.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">If speed doubles, power requirement doubles.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q8. Fuel Ratio Problem<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Day 1 Total Mass:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">60 + 100 = 160 kg<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Day 2 Total Mass:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">60 + 40 + 100 = 200 kg<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Kinetic energy \u221d mass<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Fuel consumption ratio:<br>160 : 200<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Simplified Ratio:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">4 : 5<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q9. Balanced Seesaw<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Adult weight = 2 \u00d7 Child weight<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">To balance:<br>Adult must sit at half the distance from fulcrum compared to child.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q10. Ball Thrown Upwards<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Given:<br>m = 2 kg<br>u = 20 m\/s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Sign of Work Done by Gravity<\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Upward motion \u2192 Negative<\/li>\n\n\n\n<li>Downward motion \u2192 Positive<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Work Done by Air Resistance<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Initial KE:<br>= \u00bd \u00d7 2 \u00d7 20\u00b2<br>= 400 J<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Potential Energy at top:<br>= 2 \u00d7 10 \u00d7 19.4<br>= 388 J<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Energy lost:<br>= 400 \u2212 388<br>= 12 J<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Work done by air resistance = \u221212 J<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q11. Variable Force Problem<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Speed at 0 m<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">KE = 180 J<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">180 = \u00bd \u00d7 10 \u00d7 v\u00b2<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v\u00b2 = 36<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v = 6 m\/s<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Speed at 4 m<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Work done = Area under graph<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Area = 50 \u00d7 4 = 200 J<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Final KE:<br>= 180 + 200<br>= 380 J<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">380 = \u00bd \u00d7 10 \u00d7 v\u00b2<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v\u00b2 = 76<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v \u2248 8.7 m\/s<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Negative acceleration?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No, force is always positive.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q12. Ball on Moon<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Moon gravity = Earth gravity \/ 6<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Height \u221d 1\/g<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Height on Moon:<br>= 8 \u00d7 6<br>= 48 m<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">48 m<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q13. Car Braking Problem<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Motion Between A and B<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Car moves with constant speed.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Kinetic Energy at A<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">m = 1000 kg<br>v = 35 m\/s<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">KE = \u00bd \u00d7 1000 \u00d7 35\u00b2<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">KE = 612500 J<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) Work Done by Brakes<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Work done = Change in KE<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= \u2212612500 J<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iv) Energy Transformation<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Kinetic energy converts into heat due to friction.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q14. Potential Energy Graph<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Mechanical energy remains constant.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Total energy = 30 J<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Use:<br>KE = Total Energy \u2212 PE<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Then:<br>KE = \u00bd mv\u00b2<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Students can calculate velocity using graph values.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q15. Coconut Falling Problem<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Given:<br>m = 1.5 kg<br>h = 10 m<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Velocity Before Hitting Sand<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">v\u00b2 = 2gh<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v\u00b2 = 2 \u00d7 10 \u00d7 10<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v\u00b2 = 200<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">v = 14.14 m\/s<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Depth of Depression<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Potential Energy:<br>= 1.5 \u00d7 10 \u00d7 10<br>= 150 J<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Force = 3000 N<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Depth:<br>s = W\/F<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">s = 150 \/ 3000<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">s = 0.05 m<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Depth = 5 cm<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Common Mistakes<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Forgetting SI units<\/li>\n\n\n\n<li>Using wrong formula for energy<\/li>\n\n\n\n<li>Ignoring direction in work done<\/li>\n\n\n\n<li>Confusing power with energy<\/li>\n\n\n\n<li>Not converting km\/h into m\/s<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Exam Tips<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Learn all formulas carefully.<\/li>\n\n\n\n<li>Draw diagrams for machines.<\/li>\n\n\n\n<li>Always write units in answers.<\/li>\n\n\n\n<li>Use proper sign convention for work done.<\/li>\n\n\n\n<li>Practice numerical problems regularly.<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Practice MCQs<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">1. SI unit of work is:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Newton<br>B. Joule<br>C. Watt<br>D. Pascal<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Joule<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">2. Energy possessed due to motion is:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Potential Energy<br>B. Chemical Energy<br>C. Kinetic Energy<br>D. Heat Energy<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. Kinetic Energy<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">3. Formula for power is:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. F \u00d7 s<br>B. mgh<br>C. W\/t<br>D. \u00bdmv\u00b2<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. W\/t<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">4. Mechanical advantage of a fixed pulley is:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. 0<br>B. 1<br>C. 2<br>D. 10<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. 1<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">5. Energy stored in stretched spring is:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Sound Energy<br>B. Potential Energy<br>C. Heat Energy<br>D. Light Energy<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Potential Energy<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">FAQ Section<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Q1. What is work in physics?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Work is done when force causes displacement in the direction of force.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q2. What is the SI unit of energy?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Joule (J)<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q3. What is kinetic energy?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Energy possessed by a moving object.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q4. What is potential energy?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Stored energy due to position or shape.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q5. What is a simple machine?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A device that makes work easier by changing force direction or magnitude.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Boost your Physics preparation with more chapter-wise solutions, MCQs, notes, and mock tests only on <a href=\"http:\/\/www.mymockmate.com\/\">www.mymockmate.com<\/a>. Start practicing today and score higher in your exams!<\/p>\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\/2510?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 explains the concepts of work, energy, power, and simple machines with practical<\/p>\n","protected":false},"author":3,"featured_media":2512,"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":[1359,1362,1356,1360,1357,1361,1358,1355,1354],"class_list":["post-2510","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cbse","category-class-9","category-science","tag-class-9-science","tag-inclined-plane","tag-kinetic-energy","tag-lever","tag-potential-energy","tag-power","tag-pulley","tag-simple-machines","tag-work-and-energy"],"jetpack_publicize_connections":[],"_links":{"self":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2510","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=2510"}],"version-history":[{"count":2,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2510\/revisions"}],"predecessor-version":[{"id":2651,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2510\/revisions\/2651"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media\/2512"}],"wp:attachment":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media?parent=2510"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/categories?post=2510"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/tags?post=2510"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}