Using something like a linear accelerator, could a visible object to accelerated to thousands of miles per second? I am wondering what problems would arise using the same process that accelerates protons, etc. on something as large as a bb or maybe just a grain of sand. Not sure the practical reason for this but perhaps something could be learned.
But maybe we know what would happen with a larger object. Maybe such accelerators rely on the objects not being affected as much by gravity although in a vacuum I would guess even protons would be affected by gravity just as much as a bb.
 A: The main purpose and practice of particle accelerators - like the linear or circular or magnetic induced electrodynamic particle accelerators, are damn compelling and complex, in the same regard as the history and form of our cosmos is.
The particles accelerators uses high energy electromagnetic fields to make small - usually elementary, particles to travel at very high speeds. The reason for using elementary particles or CHARGED subatomic particles, like electrons and protons, is because they are able to move at very high speed, provided with very high energies because they are stable (as in case of electrons and protons) or neutral like neutrons.
Big particles can also be accelerated to such high speeds of fractions of speed of light. Whole atoms of gold and uranium, which are much heavier, are used sometimes.
But, using large atoms or, say, objects, is still beyond practice and no object visible to naked eye, has ever been accelerated in particle accelerators.
Big particles and objects are electrically neutral so they are  not in any use of being accelerated by electromagnetic fields. The gravity also plays somewhat minute role in disturbing the stability of travel of particles much heavier than electrons and protons in vacuum tubes of accelerators. But, by using elementary particles, the mere possibility of even the effect of gravity is just shunted or nullified.
Researchers and scientists use particle accelerators to study the origins of our universe, investigate the subatomic structure of the world around us and advance research in medicine environment clean-up and more.
Recently, CERN, with the CMS collaboration, has seen the evidence of top quarks - the heaviest known elementary particle, in collision carried out between HEAVY lead-lead nuclei or ions at the Large Hadron Collider (LHC). But, the reality of being able to accelerate objects or heavy-massive particles in accelerators is still beyond theory and practicality.
