There are many examples of using smartphones in physics experiments. Students and teachers can easily perform many physics experiments with the help of smartphone sensors, even experiments for which high-cost materials are needed. There are different types of such experiments in which various kinds of sensors are used. Many physical quantities can be reliably measured with smartphone sensors after some calibration. One of the physical quantities that can be determined with these sensors is object speed. For example, the angular velocities of rotating objects have been measured with a smartphone light as well as proximity, acceleration, and magnetic field sensors. The speeds of light-emitting objects traveling on a straight path and inclined plane have also been determined with a smartphone light sensor. Ball velocities have also been determined with a smartphone oscilloscope app. In this study, we determine the speed of a toy car over a certain distance using smartphone magnetic field, light, and proximity sensors simultaneously with just one experiences.