The Marble We will say the marble that our marble is of average game size, about 3/4" diameter,$P{⋯}^{⋯}$ a fairly typical game size for a marble giving us a volume of 3.59x10${⋯}^{⋯}$ m${⋯}^{⋯}$.  Since most marbles are glass, assume ours is as well. Radius: r = diameter / 2 Volume of a sphere: $Vol = 4/3π{r}^{3}$ With the a glass density of 2500 kg per cubic meter,${}^4$ our marble has a mass of 9 grams. Density: $Mass = Volume (ρ)$ In order for the marble to have the same kinetic energy as the Bloodhound,  the marble will have to be moving at a rate of just over 980000 km/hr. At that rate, said marble would circumnavigate the earth (distance wise) in about 15 minutes.