1. Find an algebraic expression for the electric field strength E0 at the surface of a charged sphere in terms of the sphere's potential V0 and radius R. 2) What is the electric field strength at the surface of a 0.80-{\rm cm}-diameter marble charged to 550 V?

Astone is dropped from the upper observation deck of a tower, 250 m above the ground. (assume g = 9.8 m/s2.) (a) find the distance (in meters) of the stone above ground level at time t. h(t) = (b) how long does it take the stone to reach the ground? (round your answer to two decimal places.) s (c) with what velocity does it strike the ground? (round your answer to one decimal place.) m/s (d) if the stone is thrown downward with a speed of 2 m/s, how long does it take to reach the ground? (round your answer to two decimal places.) s