Joe and Sal decide that little Ronny is well-behaved enough to sit at the table with the family for Thanksgiving dinner. They are wrong. Ronny throws a 150-g handful of mashed potatoes horizontally with a speed of 5 m/s. It strikes a 1.2-kg gravy boat that is initially at rest on the frictionless table. If the potatoes stick to the gravy boat, what is the speed of the combined system as it slides down the table toward Grandpa?