"consider the following systems: i) water behind a dam. ii) a swinging pendulum. iii) an apple on an apple tree. iv) the space shuttle in orbit. in which of the systems is potential energy present? "a. i and ii b. i, ii and iii. c. ii, iii and iv. d. ii and iv .e. i, iii and iv.

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.

Scientific models are based on current knowledge, which can limit their effectiveness when new discoveries are made.

The ideal gas model is valid if which of the following conditions is true? the gas density is low. the gas density is high. the temperature is low. the temperature is high. the gas density and the temperature are low. the gas density and the temperature are high. the gas density is high and the temperature is low. the gas density is low and the temperature is high.