Have kids roll marbles on a smooth and rough surface. What surface makes the marble roll the fastest?
Sink or Float?
"Hypothesize before you perform the experiment about which liquid will move the marble faster or slower."- via ehow and science buddies
Marble Moon Craters
"The inertia of the spinning marble is a "push" force. The glass supplies another "push" force that keeps the marble moving in a "uniform circular motion." The force of the glass is centripetal force, a force that makes a body follow a curved path. The combined forces of the spinning marble and the glass create a relative force greater than gravity." - Steve Spangler