CBSE Class 11-science Answered

Dear Student

Initially total energy of Gayle  =  KE+PE = 1/2 X  mv²   +   mgh  =  1 /2  X 50 X 4² +  50X10X 15  =7900 J

Initial energy of sledge =  KE+PE= o+ 5X10 X 15  =750 J

Initially total energy of Gayle's brother = KE+PE = 1/2  X 30X 0 +  50X10X (15-5)  = 5000J

Total initial energy= 7900+750+5000= 13650 J

Final energy of both of them together with sledge =KE+PE =  1 /2  X (50+30+5) X V² +0 = 42.5  V²

Total energy conserves  ==>  13650 =42.5  V²  ==>  v²=  321.17  ==> V=  17.9 m/s

speed at the bottom of the hill if the total vertical drop is 15.0 m  =V=17.9 m/s

Regards

Team

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