I'm not sure what level of force is needed to crack a turtle shell, but hopefully a child turtle's weight at full speed isn't it. Baby turtle is pretty reckless it seems, but that's all part of being a parent: not trusting anything your kid has planned or might have planned. Pro tip for avoiding heart attacks: Assume the worst and then be pleasantly surprised the kid is still in one piece at the end of it. Nice job, boy! Arms are still attached!