Which of the following is an example of an opposing force? A. Gravity pulling a ball down a hill
B. Wind blowing a leaf off of a tree
C. Gravity holding a rock still on the ground
D. Water pushing against someone as they wade through a pool

Plss anybody know how to do this? ? i need the answers from a through d

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.

What kind of simple machine is a catapult?