The current theory of the structure of the
earth, called plate tectonics, tells us that the
continents are in constant motion.
assume that the north american continent
can be represented by a slab of rock 5100 kmon a side and 30 km deep and that the rock
has an average mass density of 2850 kg/m3
.
the continent is moving at the rate of about
3.8 cm/year.
what is the mass of the continent?
answer in units of kg.

what is the kinetic energy of the continent?
answer in units of j.

a jogger (of mass 80 kg) has the same kinetic
energy as that of the continent.
what would his speed be?
answer in units of m/s.