{"id":199295,"date":"2025-03-11T04:27:02","date_gmt":"2025-03-11T04:27:02","guid":{"rendered":"https:\/\/learnexams.com\/blog\/?p=199295"},"modified":"2025-03-11T04:27:04","modified_gmt":"2025-03-11T04:27:04","slug":"a-police-officer-is-called-in-for-accident-reconstruction","status":"publish","type":"post","link":"https:\/\/www.learnexams.com\/blog\/2025\/03\/11\/a-police-officer-is-called-in-for-accident-reconstruction\/","title":{"rendered":"A police officer is called in for accident reconstruction"},"content":{"rendered":"\n<p>A police officer is called in for accident reconstruction. He measures 11-meter long skid marks and he knows that for that particular tire\/pavement combination, the coefficient of kinetic friction is 0.65. He also knows that the car was traveling at 3.5 m\/s just before impact (the end of the skid marks). What was the speed of the car before it began the skid? Convert this to miles per hour. (Note: 1 mile = 1609 meters).<\/p>\n\n\n\n<p><mark style=\"background-color:rgba(0, 0, 0, 0)\" class=\"has-inline-color has-ast-global-color-6-color\"><strong>The correct answer and explanation is :<\/strong><\/mark><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" src=\"https:\/\/learnexams.com\/blog\/wp-content\/uploads\/2025\/03\/image-830-1024x614.png\" alt=\"\" class=\"wp-image-199296\"\/><\/figure>\n\n\n\n<p>The initial speed of the car before it began to skid was <strong>12.35 m\/s<\/strong>, which converts to approximately <strong>27.63 mph<\/strong>.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p>When a vehicle skids, its speed is reduced due to the force of friction between the tires and the road surface. To determine the initial speed before skidding, we use the <strong>kinematic equation<\/strong>:<\/p>\n\n\n\n<p>[<br>v^2 = u^2 + 2as<br>]<\/p>\n\n\n\n<p>where:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>( v = 3.5 ) m\/s (final speed, just before impact),<\/li>\n\n\n\n<li>( u ) = initial speed before the skid (to be determined),<\/li>\n\n\n\n<li>( a = -\\mu g ) (deceleration due to friction),<\/li>\n\n\n\n<li>( s = 11 ) m (skid mark length),<\/li>\n\n\n\n<li>( \\mu = 0.65 ) (coefficient of kinetic friction),<\/li>\n\n\n\n<li>( g = 9.81 ) m\/s\u00b2 (acceleration due to gravity).<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">Step-by-step Calculation:<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Compute the deceleration due to friction:<br>[<br>a = &#8211; (0.65 \\times 9.81) = -6.3765 \\text{ m\/s\u00b2}<br>]<\/li>\n\n\n\n<li>Solve for ( u ):<br>[<br>u = \\sqrt{v^2 &#8211; 2as}<br>]<br>[<br>u = \\sqrt{(3.5)^2 &#8211; (2 \\times (-6.3765) \\times 11)}<br>]<br>[<br>u = \\sqrt{12.25 + 140.283}<br>]<br>[<br>u = \\sqrt{152.533} = 12.35 \\text{ m\/s}<br>]<\/li>\n\n\n\n<li>Convert to miles per hour (mph):<br>[<br>12.35 \\times \\frac{3600}{1609} \\approx 27.63 \\text{ mph}<br>]<\/li>\n<\/ol>\n\n\n\n<h3 class=\"wp-block-heading\">Conclusion:<\/h3>\n\n\n\n<p>The car was traveling at approximately <strong>12.35 m\/s (27.63 mph)<\/strong> before it began to skid. This analysis helps in accident reconstruction to determine whether the driver was speeding or following traffic regulations.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A police officer is called in for accident reconstruction. He measures 11-meter long skid marks and he knows that for that particular tire\/pavement combination, the coefficient of kinetic friction is 0.65. He also knows that the car was traveling at 3.5 m\/s just before impact (the end of the skid marks). What was the speed [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[25],"tags":[],"class_list":["post-199295","post","type-post","status-publish","format-standard","hentry","category-exams-certification"],"_links":{"self":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/199295","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/comments?post=199295"}],"version-history":[{"count":0,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/posts\/199295\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/media?parent=199295"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/categories?post=199295"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.learnexams.com\/blog\/wp-json\/wp\/v2\/tags?post=199295"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}