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.

This problem has been solved! see the answera non-uniform fire escape ladder is 6.0m long whenextended to the icy alley below. it is held at the top by africtionless pivot, and there is neglibible frictional force fromthe icy surface at the bottom. the ladder weighs 250n, and it'scenter of gravity is 2.0m along the ladder from the bottom. amother and child of total weight 750n are on the ladder 1.5m fromthe pivot. the ladder makes an angle θ with the horizontal.find the magnitude and direction ofa) the force exerted by the icy alley on the ladderb) the force exerted by the ladder on the pivotc) do your answers in part a and b depend on the angle?

Describe different biomes. what are some adaptations that organisms (plants or animals) must have to live in each biome?

A1-lb collar is attached to a spring and slides without friction along a circular rod in a vertical plane. the spring has an undeformed length of 5 in. and a constant k =25 lb/ft. knowing that the collar is released from being held at a determine, the speed of the collar and the normal force between the collar and the rod as the collar passes through b.