Sam collects toy trains. Several of his trains operate using invisible forces such as gravity, magnetism, and electricity.
Sam invites his new friend, Ben, over to play with his magnetic train set. As Sam starts to create a train, Ben asks him how he knows how to put the cars together so they will stay together when the train is pulled. Sam says it is all about invisible forces! Ben decides to investigate. He begins by taking two train pieces with magnets on both ends and arranges them in different patterns to see if they will connect. His observations are recorded in the chart below.