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6. A car of mass 1000 kg travelling at 30 m/s stops aftera distance of 50 m, decelerating uniformly. What isthe force exerted by it on the brakes? What is thework done by the brakes? Ans. 9000 N, 4.5 x 105

Answer»

Givenm=1000kgu=30m/ss=50m v=0

v^2-u^2=2asa =( v^2-u^2)/2sa= (0^2-30^2)/2×50a= -900/100a= -9m/s^2retardation=9m/s^2

Force exerted by brakes = Mass×Retardation =1000×9 =9000N (Ans)

Work exerted by brakes = Retarding force×Displacement = 9000×50 = 4.5×10^5J (Ans)



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