At fixed speed and gamma, mass scales momentum, total energy, and kinetic energy together. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Three kilograms give a twenty-unit momentum

With gamma 5/3, mass 3 kg, and speed 4 m/s, momentum is 20 kg m/s. Total energy is 125 J and kinetic energy is 50 J.

5334=20K=12575=50\frac{5}{3}\cdot3\cdot4=20\quad K=125\,-\,75=50
Relativistic energyRest energy and motion energy form a triangle.speedquiet leglimitbetagammarest energymotion energytotal energykinetic energy

Six kilograms double the momentum and energy

Mass 6 kg gives momentum 40 kg m/s, total energy 250 J, and kinetic energy 100 J.

5364=40K=250150=100\frac{5}{3}\cdot6\cdot4=40\quad K=250\,-\,150=100
Relativistic energyRest energy and motion energy form a triangle.speedquiet leglimitbetagammarest energymotion energytotal energykinetic energy

Nine kilograms triple the first-row ledgers

Mass 9 kg gives momentum 60 kg m/s, total energy 375 J, and kinetic energy 150 J. The scan changes mass while speed and gamma stay fixed.

5394=60K=375225=150\frac{5}{3}\cdot9\cdot4=60\quad K=375\,-\,225=150
Relativistic energyRest energy and motion energy form a triangle.speedquiet leglimitbetagammarest energymotion energytotal energykinetic energy