Lunch on Wheels
The robotics team at Cedar Ridge Middle School built a small wheeled robot that carries lunch from the cafeteria to the library, where a study group eats. The trip, with its stops, takes about 30 minutes. In early trials the soup arrived only lukewarm. Team captain Imani Brooks set a goal: the soup must still be at least 60 °C when it arrives. There is also a limit. The robot's motors struggle with heavy loads, so the empty food compartment can have a mass of no more than 350 g.
The team built five compartments from the same size of plastic box and changed only the lining and the lid. Design A had no lining. Design B had a foam lining 2 cm thick. Design C had a lining of aluminum foil. Design D had the same foam lining as B with a layer of foil on the inside. Design E had the same foam lining as B, but its lid had a 2 cm gap where a sensor cable passed through.
Hot water stood in for soup, so no food was wasted during testing. For each test, the teacher poured 500 mL of water at 70 °C into a sealed jar and placed it in the compartment. The robot then drove the same 30-minute route along the same hallway, which stayed at about 22 °C. When the robot arrived, a student opened the lid and read the water temperature with a probe thermometer. The team tested each design three times. The table shows the average results.