A very long train is rolling at 4 m/s along a straight track. An observer is standing on the ground very dangerously close to the train as moves past notices a person standing on top of a car. When the person on the car is 300 m from the observer, the person begins running toward the observer at 6 m/s. A. Please write down the velocity vector equation for the person with respect to the ground.
B. How much time does the person take to reach the observer?

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.