1.) An insulating rod having linear charge density 40 uC/m and linear mass desnity u = 0.1 kg/m is released from rest in a uniform electric field E = 100V/m directed perpendicular to the rod. What is speed of the rod after travelling 2.00m? In previous questions, i used the formulas V = -Ed, where E is the magnitude of the electric field and d is the distance from the point charge. V would give me the potential (or electric potential) of the field. However, here i have strange values like "linear charge density" and "unfiform electric field". How do i deal with these ?? 2.) Two insulating spheres have radii 0.30 cm and 0.50 cm with masses 0.1kg and 0.7kg. The charges are evenly distributed with values -2.00 uC and 3.00 uC. They are released from rest when their centers are seperated by 1.0m. a.) How fast are they moving when they collide? I immediately thought that somehow i will have to use conservation of momentum. But setting up my equation: [tex]m_1v_1 + m_2v_2 = m_t * v_t [/tex] (where mt and vt are combinded mass and velocity). Where do i go from here? Thank you.