What work needs to be done to get the carriage. with a mass of 70 tons, moving at a speed of 2.0 m / s

What work needs to be done to get the carriage. with a mass of 70 tons, moving at a speed of 2.0 m / s, should a speed of 4 m / s be reported?

Initial data: m (wagon weight) = 70 t = 70 * 10 ^ 3 kg; V1 (initial speed of the car) = 2 m / s, V2 (speed that the car should develop) = 4 m / s.

The work that needs to be done in order for the car to reach the required speed will be equal to the difference in kinetic energies: A = Ek2 – Ek1 = m * V2 ^ 2/2 – m * V1 ^ 2/2 = 0.5 * m * (V22 – V12 ).

Calculation: A = 0.5 * 70 * 10 ^ 3 * (42 – 22) = 35 * 10 ^ 3 * (16 – 4) = 35 * 10 ^ 3 * 12 = 420 * 10 ^ 3 J = 420 kJ.

Answer: You need to do a job of 420 kJ.