A 10 kg truck slides down a slide. It begins 12 m above the ground from rest and experiences no friction. Use the principle of conservation of mechanical energy,
a. to calculate its speed when he is at point B.
b. To calculate height at point C if its velocity is 5 m/s.

Along the line connecting the two charges, at what distance from the charge q1 is the total electric field from the two charges zero? express your answer in terms of some or all of the variables s, q1, q2 and k =14ï€ïµ0. if your answer is difficult to enter, consider simplifying it, as it can be made relatively simple with some work.