Explanation: A pebble has the same density and a boulder when it rolls down a hill. The pebble will most-likely roll down very fast which can make it dense.
I really hope this helped! like at all...
Truthfully, I don't know a lot of this type of stuff.. But worth a shot, right?
This statement can be true because the pebble and the huge boulder are made up from the same compound of materials meaning they will most likely have the same hardness when measured
