VWR* Visual Scientifics Photogate Sensor, Four Modes: Gate, Pulse, Pendulum, Frequency, also Works with VISUAL SCIENTIFICS and numerous physical science systems, This kit contains: 2 Photogates, 2Connecting wires, Main photogate hub and control, Wall charger
Square Friction Cube With Hook, 4 Surfaces, 2 Inch, Provides Four Surfaces For Exploration Into The Force Of Friction. Each Side Of The 2in Cube Provides A Surface (Wood, Paper, Vinyl, Sandpaper) With A Different Coefficient Of Friction