A 25 kg mass moving with 25 m/s is brought to a complete stop with a constant deceleration over a period of 5 seconds by a brake system. The brake energy is absorbed by 0.5kg water initially at 100 kPa, 20°C. Assume that the mass is at constant P and T. Find the energy the brake removes from the mass assuming P = C.

Correct Answer: 7.8125 kJ
E2 – E1= ∆E = 0.5 mV2 = 0.5 × 25 × 25^(2)/1000 = 7.8125 kJ.