Each time a ball bounces, gravity reverses. Will it reach relativistic speeds?

No, gravity creates a constant increase in speed per second, that fherefore will be smaller after wvery bounce. (At higher speeds, the ball will have a shorter time before it reaches its next bounce.)

The 10% speed loss however will increase while speed increases. So the speed loss each bounce will increase, while the speed increase will decrease between each bounce. These will converge.

And congrats on 10K!

Gravity is a constant. It does not reverse.

Just hypothetically, let’s imagine gravity can reverse, and such a reversal happens to be triggered by our gravity reversing ball. We drop the ball from 100 feet above the ground. Gravity being in normal mode, the ball falls, accelerating at 32 ft/s² till it it hits the ground. It rebounds upward and gravity now reverses, causing the ball to accelerate as it travels upward. Initially it accelerates at 32 ft/s² but its acceleration curve is asymptotic because gravity drops off as the inverse-square of distance between the object it is acting on (our gravity reversing ball) and the mass producing the gravitational tug (or in our reversed gravity case, gravitational repulsion). So the ball’s acceleration (along with everything else on Earth) would decrease as it moved outward through the solar system and eventually other gravitational forces of nearer massive objects would more than override the ever shrinking repulsive force from the Earth.

Let me state that I find the idea of reversible gravity quite repulsive. Having it would definitely take the bounce out of my each step on earth.

Well… (aw here it goes again)

Kinetic energy is .5*m*v^2, so when it loses 10% of its energy, it’s really only losing 10% of v^2, not 10% of its velocity. So when it reverses, its rebound velocity will be sqrt(.9) times the velocity at which it hit the floor/ceiling, right? Which is more like 95% of the velocity.

On the other hand, gravity will increase its velocity which each bounce, and to answer our question we need to know whether this percent increase is larger or smaller than the percent loss. Here’s the relevant kinematics equation:

vf^2 = vi^2 + 2ad where d = 8ft, a = 32ft/s/s

You can see readily that vf will not increase by a fixed percentage each time, since the term that increases the speed, 2ad, is added, not multiplied. As vi gets increasingly large, 2ad will be become negligible, and the 5% loss of speed that it suffers each time will be much, much more impactful.

So no, speed can’t increase unboundedly into relativistic quantities.

Gravity does not reverse, the ball flexes as a result of an interaction to the floor, @ETpro is right. If you could reverse gravity, the invention would be worth an obscenely large sum of money.

@Ron_C @Rarebear This is merely hypothetical. I know that gravity can’t reverse. Hopefully you didn’t actually think that I actually thought that gravity could reverse.

@Mariah We can probably shortcut the whole infinite series thing. When the energy added in the journey between the two walls is equal to the energy lost in each bounce, then that is the equilibrium.

@PhiNotPi heh, I don’t even ask hypothetical questions here anymore because invariably one of the first answers is “it couldn’t happen”

@PhiNotPi It was not clear from your question that you understood that.

@PhiNotPi My bad for not reading all the question details. I completely overlooked the point of their being a ceiling.

[ deleted by me – wrong answer ]

Matter cannot reach relativistic velocities, inertial mass increase exponentially when velocity increase. Cannot reverse gravity either, Several impossibilities at question.