For each of the following, assume the object in question is in “free fall”, meaning it is accelerating downward solely due to the effect of gravity. A stone is dropped from a height of 12m and falls to a pond below. What is the amount of time that passes before the stone hits the pond?

A second stone is thrown straight down toward the same pond of the same height. It hits the water in 1.0. What is the initial velocity?

When a charged balloon sticks to a wall, the downward gravitational force is balanced by an upward static friction force. the normal force is provided by the electrical attraction between the charged balloon and the equal but oppositely charged polarization induced in the wall's molecules. if the mass of a balloon is 1.2 g, its coefficient of static friction with the wall is 0.71, and the average distance between the opposite charges is 0.80 mm, what minimum amount of charge must be placed on the balloon in order for it to stick to the wall? express your answer to two significant figures and include appropriate units.