Could you reversibly control the mass of a box of self-propelled nanoballs by increasing their speed?

Question

Exploring the nature of confined energy giving rise to "mass" or gravitation,

My assumptions:

• Most of my own mass is from the confinement of baryonic quarks in the strong force
• A bunch of photons in a mirror box makes the box weigh more
• All types of confined pressure actually produce a gravitational effect
• This is because the inner force trajectories accumulate on the wall against the external force as the container is put into motion (more particles hit the ground as you lift, and less hit the ceiling)
• But for massless particles, it's just the actual confinement of relativistic mass on a small/finite space? Might have lost on those last 2.

Based on that, I feel like the answer is trivial- yes, a box with plenty and fast enough wirelessly controllable bouncing nanoballs that each propel themselves in the direction of their current motion, would increment the displayed weight on a scale as you increased the propulsion force of the balls, while the weight would decrement as you decreased the propulsion of the balls.

Answer 1

If the box is a closed system, the mass-energy cannot increase as it is a conserved quantity.

The question considers self-propelled nanoballs. However, this propulsion cannot be generated from nothing: the nanoballs must carry some kind of fuel to propel themselves, or else draw energy from their surroundings. If the system is closed, any increase in energy due to the nanoballs' motion must be equal to the decrease in energy of the propelling agent.

If energy is somehow pumped in from the outside, then yes, the mass-energy will increase. But you don't need nanoballs for this effect to be seen.