Locomotion abilities are best studied for "Tyrannosaurus", and there are two main issues concerning this: how well it could turn; and what its maximum straight-line speed was likely to have been. "Tyrannosaurus" may have been slow to turn, possibly taking one to two seconds to turn only 45° – an amount that humans, being vertically oriented and tail-less, can spin in a fraction of a second. The cause of the difficulty is rotational inertia, since much of "Tyrannosaurus"s mass was some distance from its center of gravity, like a human carrying a heavy timber.