The current theory of the structure of the Earth, called plate tectonics, tells us what the continents are in constant motion. Assume that the North American continent can be represented by a slab of rock 5850km on a side and 35km deep and that the rock has an average mass density of 2750kg/m^3. The continent is moving at the rate of about 3.2cm/year. what is the kinetic energy of the continent ? answer in the units of J