1. Work-Kinetic E: With brakes fully applied, a 1420 kg cardecelerates from a sp

Question

1. Work-Kinetic E: With brakes fully applied, a 1420 kg cardecelerates from a speed of 80.0 km/hr. What is the work done by the braking force in bringingthe car to a stop? What is the changein the kinetic energy of thecar? 2. VariableForce: A particlemoves along the x axis under the influence of a variable force F(x)= 5.8x2 + 4.9x where the force ismeasured in Newtons and the distance inmeters. What is the potential energy associated with this force atx = 2.0m? Assume that U(x) =0 J at x = 0 m. 1. Work-Kinetic E: With brakes fully applied, a 1420 kg cardecelerates from a speed of 80.0 km/hr. What is the work done by the braking force in bringingthe car to a stop? What is the changein the kinetic energy of thecar? 2. VariableForce: A particlemoves along the x axis under the influence of a variable force F(x)= 5.8x2 + 4.9x where the force ismeasured in Newtons and the distance inmeters. What is the potential energy associated with this force atx = 2.0m? Assume that U(x) =0 J at x = 0 m.

Explanation / Answer

Potential energy               U = - integral ( F*dx)                   = - integral ( (5.8x2 + 4.9x) dx )                   = - ( 5.8 x3/3 ) - 4.9(x2/2)    Now applying limits from x = 0 to x = 2 and finally weget            U (x =2) = 25.26J

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