One thing you should notice. It is kind of weird. Ke has no direction so that fact that it has velocities associated with it does not matter. It becomes a scaler (something measured by amount alone).
General Formula Ke = 1/2 m v^2 Formula for this problem Ke = 1/2 m (v2)^2 - 1/2 m (v1)^2
Givens m = 1200 kg v2 = 100 km/hr = 100 km/h * [1 hour / 3600 sec] * [1000 m/ 1km] = 27.8 m/s v1 = 50 km / hr = 13.9 m/s
Substitution and work. ================ delta Ke = 1/2 1200 (27.8)^2 - 1/2 1200 (13.9)^2 delta Ke = 463704 - 115926 delta Ke = 34778 Joules delta Ke = 34.8 kJ
The change is 34.8 kJ which means that the vehicle gains 34.8 kJ
