225_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

225_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

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Unformatted text preview: Sec_2.8-2.12.qxd 9/25/08 11:44 AM Page 219 SECTION 2.8 Impact Loading Problem 2.8-10 A bumping post at the end of a track in a railway yard has a spring constant k 8.0 MN/m (see figure). The maximum possible displacement d of the end of the striking plate is 450 mm. What is the maximum velocity max that a railway car of weight W 545 kN can have without damaging the bumping post when it strikes it? Solution 2.8-10 Bumping post for a railway car STRAIN ENERGY WHEN SPRING IS COMPRESSED TO THE MAXIMUM ALLOWABLE AMOUNT U kd2 max 2 kd2 2 CONSERVATION OF ENERGY KE k 8.0 MN/m d maximum displacement of spring d Find max W 545 kN 450 mm v vmax KINETIC ENERGY BEFORE IMPACT KE Wv2 2g vmax kd2 2 v 2 A W/g d kd2 W/g k ; A (545 kN)/(9.81 m/s2) SUBSTITUTE NUMERICAL VALUES: max Mv2 2 U Wv2 2g 8.0 MN/m (450 mm) 5400 mm/s 5.4 m/s Problem 2.8-11 A bumper for a mine car is constructed with a spring of stiffness k 1120 lb/in. (see figure). If a car weighing 7 mph when it strikes the 3450 lb is traveling at velocity spring, what is the maximum shortening of the spring? ; v k 219 ...
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This note was uploaded on 12/22/2011 for the course MEEG 310 taught by Professor Staff during the Fall '11 term at University of Delaware.

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