Four uniform objects having the same mass and diameter are released simultaneously from rest at the same distance above the bottom of a hill and roll down without slipping. the objects are a solid sphere, a solid cylinder, a hollow cylinder and a thin-walled hollow cylinder. which of these objects will be the last one to reach the bottom of the hill?

The one with the majority of its mass furthest away from its center will reach the bottom last. The thin walled cylinder has all of its mass at the edge of itself, meaning its mass is the furthest from its center. If we take a look at the solid cylinder, it has some mass at its edge, but it also has a lot of mass very close to its center so it will roll faster than the thin walled cylinder. And the thin walled cylinder will be slower than the normal hollow cylinder because even though the hole cylinder doesn't have any mass at its center it does have some mass closer to its center than the thin walled cylinder.

So the last one to reach the bottom is the thin walled cylinder.

The answer is frictional force