Storm clouds may build up large negative charges near their bot- tom edges. The earth is a good conductor, so the charge on the clouds attract an equal and opposite charge on the earth under the cloud. The electric field strength near the earth depends on the shape of the earth's surface, as we can explain with a simple model. The top metal plate in the figure has a uniformly distributed negative charge The bottom metal plate, which has a high point, has an equal and opposite charge that is free to move.

a. What is the correct sketch of the two plates and the region between them, showing the distribution of positive charge on the bottom plate and electric field lines between the two plates with the correct direction of the field?
b. Complete your diagram by sketching electric field lines between the two plates. Where is the field strongest?
c. Explain why it is more dangerous to be on top of a hill or mountain during a lightning storm than on level ground.

Astudent throws a water balloon with speed v0 from a height h = 1.76 m at an angle θ = 21° above the horizontal toward a target on the ground. the target is located a horizontal distance d = 9.5 m from the student’s feet. assume that the balloon moves without air resistance. use a cartesian coordinate system with the origin at the balloon's initial position. (a) what is the position vector, rtarge t, that originates from the balloon's original position and terminates at the target? put this in terms of h and d, and represent it as a vector using i and j. (b) in terms of the variables in the problem, determine the time, t, after the launch it takes the balloon to reach the target. your answer should not include h. (c) create an expression for the balloon's vertical position as a function of time, y(t), in terms of t, vo, g, and θ. (d) determine the magnitude of the balloon's initial velocity, v0, in meters per second, by eliminating t from the previous two expressions.