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The composition of meters shown in Figure traffic to 72,4 km/h when the brakes of the wheels A and B were activated, causing the derailment. Determine (a) the distance traveled by the rest and (b) the force in each coupling. The coefficient of kinetic friction between the wheels and rails is 0,30.

Answer:

(a) 98,1 m

(b) FAB = 2,4x10^4 N; FBC = 5,6x10^4 N

My solution:

(a) Kinetic energy:

T = 1/2mv^2 = 1,83x10^7 J

Work:

U = (PT - FT).x

PT (Total weight) = 89x10^4

FT (Total force of friction) = 2,67x10^5

U = 6,23x10^5x

x = T / U = 29,44m Is not the correct answer

Answer:

(a) 98,1 m

(b) FAB = 2,4x10^4 N; FBC = 5,6x10^4 N

My solution:

(a) Kinetic energy:

T = 1/2mv^2 = 1,83x10^7 J

Work:

U = (PT - FT).x

PT (Total weight) = 89x10^4

FT (Total force of friction) = 2,67x10^5

U = 6,23x10^5x

x = T / U = 29,44m Is not the correct answer