A wagon with a mass of 50t moves at a speed =36km/h. By how much does the internal energy of the brakes of the wagon increase at its complete braking, if 60% of the kinetic energy is converted into internal.
The initial amount of kinetic energy was:
where "m = 50t = 5\\times10^4kg" is the mass, and "v = 36km\/h = 10m\/s" is the initial speed. The final kinetic energy is 0 (since the wagon stops completely). If 60% of the kinetic energy is converted into internal, then the result internal energy increase is:
Answer. 1.5 MJ.
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