s ▁b ary center . ▁ ▁Center ▁of ▁Gra vity ▁at ▁Work , ▁video ▁showing ▁objects ▁clim bing ▁up ▁an ▁incl ine ▁by ▁themselves . ▁ ▁Category : Class ical ▁mechan ics ▁Category : M ass ▁Mass <0x0A> </s> ▁Robert ▁" Bob " ▁Living ston ▁Arm strong ▁( 1 8 5 0 ▁– ▁ 1 9 1 7 ) ▁was ▁an ▁American ▁professional ▁baseball ▁player . ▁He ▁played ▁ 1 2 ▁of ▁ 2 1 ▁games , ▁eleven ▁in ▁center ▁field , ▁for ▁the ▁Fort ▁Wayne ▁K ek ion gas ▁in ▁the ▁first ▁professional ▁league , ▁the ▁ 1 8 7 1 ▁National ▁Association ▁of ▁Professional ▁Base ▁Ball ▁Play ers ▁( N AP BB P ). ▁ ▁Pre viously ▁Arm strong ▁played ▁three ▁seasons ▁for ▁the ▁Maryland ▁club ▁of ▁Baltimore , ▁Maryland ▁in ▁the ▁National ▁Association ▁of ▁Base ▁Ball ▁Play ers . ▁The ▁Mary lands ▁were ▁a ▁strong ▁club ▁among ▁the ▁hundreds ▁of ▁N AB B P ▁members ▁but ▁a ▁weak ▁club ▁among ▁the ▁twelve ▁that ▁cont ested ▁the ▁first ▁professional ▁p enn ant ▁race ▁in ▁ 1 8 6 9 , ▁or ▁the ▁second ▁one ▁in ▁ 1 8 7 0 . ▁ ▁Bob ▁Arm strong ▁was ▁the ▁son ▁of ▁John ▁Hor atio ▁Arm strong ▁and ▁Caroline ▁Am elia ▁Sch eld t ▁and ▁great ▁grand son ▁of ▁John ▁Arm strong ▁Jr .. ▁He ▁was ▁ 6 ' ▁ 2 " ▁and ▁was ▁married ▁to ▁Betty ▁Arnold . ▁Arm strong ▁was ▁a ▁Baltimore ▁native ▁like ▁most ▁of ▁his ▁Maryland ▁team m ates .