{"id":512,"date":"2019-08-09T15:57:18","date_gmt":"2019-08-09T10:27:18","guid":{"rendered":"https:\/\/www.physicsacademyonline.com\/blog\/?p=512"},"modified":"2021-02-25T14:02:33","modified_gmt":"2021-02-25T08:32:33","slug":"solve-jee-main-2018-with-a-smile-i","status":"publish","type":"post","link":"https:\/\/www.physicsacademyonline.com\/blog\/jee-main\/solve-jee-main-2018-with-a-smile-i.html","title":{"rendered":"SOLVE JEE (MAIN) 2018 WITH A SMILE &#8211; IV"},"content":{"rendered":"<h3 style=\"font-size: 1.20em; font-weight: normal !important;\"><i>Let <em><del>Us<\/del> <\/em><\/i><span style=\"font-family: impact; letter-spacing: 1.5px; font-size: 24px; color: #000;\">YOU<\/span><i> Solve Physics JEE (MAIN) 2018 Physics Paper<\/i><\/h3>\n<p>We continue with JEE (Main) 2018, Paper-1, Part-A: Physics. All questions are of MCQ type, with one option correct. <em>Only<\/em> after you finish a question, compare and confirm your method and answer with the video solution given at the bottom. The video is given for checking purpose alone. You are strongly advised not to see it before you solve the question yourself.<\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"text-decoration: underline;\"><strong>Question 11:<\/strong><\/span> The mass of a hydrogen molecule is 3.32 x 10<sup>-27<\/sup> kg. If 10<sup>23<\/sup> hydrogen molecules strike, per second, a fixed wall of area 2 cm\u00b2 at an angle of 45\u00b0 to the normal, and rebound elastically with a speed of 10<sup>3<\/sup> m\/s, then the pressure on the wall is nearly:<\/p>\n<p style=\"text-align: justify;\">(1) 2.35 x 10<sup>3<\/sup> N\/m\u00b2\u00a0\u00a0 \u00a0 \u00a0\u00a0\u00a0\u00a0 (2) 4.70 x 10<sup>3<\/sup> N\/m\u00b2\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 (3) 2.35 x 10<sup>2<\/sup> N\/m\u00b2\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 (4) 4.70 x 10<sup>2<\/sup> N\/m\u00b2<\/p>\n<p>&nbsp;<br \/>\nFor an oblique elastic collision in two dimensions, the component of velocity vector parallel to the wall does not change, while the component perpendicular to the wall reverses direction without change in magnitude.\u00a0Interested students may study in details from: <em> <span style=\"color: #8270a4;\">Chapter Name \u2013 Mechanics; Category \u2013 Basic; Topic Name \u2013 Impulse, Collision, and Centre of Mass; Video Name \u2013 Collision in Two Dimensions.<\/span><\/em><\/p>\n<p>What is the change in linear momentum of a molecule after a collision? What is change in linear momentum of the wall after the collision?\u00a0For a timely reminder, watch:\u00a0 <em><span style=\"color: #8270a4;\">Chapter Name \u2013 Mechanics; Category \u2013 Basic; Topic Name \u2013 Impulse, Collision, and Centre of Mass; Video Name \u2013 Principle of Conservation of Linear Momentum, and Some Applications.<\/span><\/em><\/p>\n<p>What is the momentum change of the wall per second? What is the force on the wall? You find the connection here: <em><span style=\"color: #8270a4;\">Chapter Name \u2013 Mechanics; Category \u2013 Basic; Topic Name \u2013 Newton&#8217;s Laws of Motion; Video Name \u2013 Newton&#8217;s Second Law.<\/span><\/em><\/p>\n<p>What is the pressure on the wall?<\/p>\n<p>By the way, the question is modelled on a similar theoretical derivation, here: <em><span style=\"color: #8270a4;\"> Chapter Name \u2013 Heat and Thermodynamics; Category \u2013 Basic; Topic Name \u2013 Kinetic Theory of Gases and Properties of Vapour; Video Name \u2013 Pressure Exerted by an Ideal Gas.<\/span><\/em><\/p>\n<p>&nbsp;<\/p>\n<p><iframe loading=\"lazy\" width=\"740\" height=\"416\" src=\"https:\/\/www.youtube.com\/embed\/0sZ_b8CNJmw?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"text-decoration: underline;\"><strong>Question 12:<\/strong><\/span> A silver atom in a solid oscillates in simple harmonic motion with a frequency of 10<sup>12<\/sup>\/s. What is the force constant of the bonds connecting one atom with the other? Molecular mass of silver is 108, and Avogadro&#8217;s number is 6.02 x 10<sup>23<\/sup> \/mol.<\/p>\n<p>(1) 6.4 N\/m\u00a0\u00a0 \u00a0 \u00a0 \u00a0(2) 7.1 N\/m\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 (3) 2.2 N\/m\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0(4) 5.5 N\/m<\/p>\n<p>&nbsp;<br \/>\nThe bond connecting two atoms behaves like an ideal spring. Therefore, a silver atom at the end of a bond is a prototype of spring-block system. What is the force constant of a spring?\u00a0? If you need the basics, study from here: <em><span style=\"color: #8270a4;\">Chapter Name \u2013 Mechanics; Category \u2013 Basic; Topic Name \u2013 Work and Energy; Video Name \u2013 Work Done by Spring Force.<\/span><\/em><\/p>\n<p>What is the formula for frequency of the simple harmonic motion? For reference: <em> <span style=\"color: #8270a4;\">Chapter Name \u2013 Mechanics; Category \u2013 Advanced; Topic Name \u2013 Gravitation; Video Name \u2013 Advanced-Level Problems on Gravitation II (problem 2).<\/span><\/em><\/p>\n<p>Using given data, what is the mass of a silver atom in standard SI unit? Unless your Chemistry is strong, you will need this: <em><span style=\"color: #8270a4;\">Chapter Name \u2013 Heat and Thermodynamics; Category \u2013 Basic; Topic Name \u2013 Thermal Expansion; Video Name \u2013 Expansion of Gases II.<\/span><\/em><\/p>\n<p>Substituting known values will lead you to the correct choice.<\/p>\n<p>&nbsp;<\/p>\n<p><iframe loading=\"lazy\" width=\"740\" height=\"416\" src=\"https:\/\/www.youtube.com\/embed\/_HNVG8SEwV0?feature=oembed\" frameborder=\"0\" allow=\"accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture\" allowfullscreen><\/iframe><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Let Us YOU Solve Physics JEE (MAIN) 2018 Physics Paper We continue with JEE (Main) 2018, Paper-1, Part-A: Physics. All questions are of MCQ type, with one option correct. Only&#8230;<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13,26],"tags":[],"_links":{"self":[{"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/posts\/512"}],"collection":[{"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/comments?post=512"}],"version-history":[{"count":34,"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/posts\/512\/revisions"}],"predecessor-version":[{"id":635,"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/posts\/512\/revisions\/635"}],"wp:attachment":[{"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/media?parent=512"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/categories?post=512"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.physicsacademyonline.com\/blog\/wp-json\/wp\/v2\/tags?post=512"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}