Two blocks A and B of masses m $$=$$ $$10$$ kg and M $$=$$ $$20$$ kg respectively are placed on each other and their combination rests on a fixed horizontal surface C. A light string passing over the smooth light pulley is used to contact A and B as shown. The coefficient of sliding friction between all surfaces in contact is μ $$=$$ $$14$$. If A is dragged with a force F then for both A and B to move with a uniform speed , the value of F should be

Question

Two blocks A and B of masses m $$=$$ $$10$$ kg and M $$=$$ $$20$$ kg respectively are placed on each other and their combination rests on a fixed horizontal surface C. A light string passing over the smooth light pulley is used to contact A and B as shown. The coefficient of sliding friction between all surfaces in contact is μ $$=$$ $$14$$. If A is dragged with a force F then for both A and B to move with a uniform speed , the value of F should be

Infinity Learn · Accepted Answer

$$f1=Frictional$$ force on $$A=10$$×$$10$$×$$14N=25$$ N $$f2=Frictional$$ force acting on B $$=(10+20)$$×$$10$$×$$14N=75$$ N For A $$T-f1=0$$ ⇒$$T=25$$ N For B, $$F-f1-f2-T=0$$ ⇒F $$=(25+75+25)N$$ $$=125$$ N

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