Two \(5000-\mathrm{kg}\) freight cars roll without friction (one) at \(1 \mathrm{~m} / \mathrm{s}\), the other at \(2 \mathrm{~m} / \mathrm{s}\) ) toward each other on a level track. Thus one car's kinetic energy is \(2500 \mathrm{~J}\) and the other's is \(10,000 \mathrm{~J}\), Before they collide their total kinetic energy is
A. \(1250 \mathrm{~J}\) B. \(2500 \mathrm{~J}\) C. \(7500 \mathrm{~J}\) D. \(12,500 \mathrm{~J}\)
