In this challenge, kids modify a paper cup so it can zip down a line and drop a marble onto a target. Students will follow the engineering design process to modify a cup to carry a marble down a zip line; attach a string to tip the cup; test their cup by sliding it down the zip line, releasing the marble, and trying to hit a target on the floor; and improve their system based on testing results. Download this activity en Español Materials 9 feet (3m) of smooth line (e.g., fishing line or kite s