Question

The curre 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 4700 km on a side and 28 km deep and that the rock has an average mass density of 2940 kg / (m ^ 3) The continent is moving at the rate of about 4.2 cm / y * e * a * r . What is the mass of continent ? Answer in units of kg
What is the kinetic energy of the continent
a jogger (75kg) has the same kinetic energy what would his speed be?

Answer 1

a)     $Mass= average density(ℓ)* slab rock (a^2) * depth (h) Mass= (ℓ)(a^2) (h)$ $Mass= average density(ℓ)* slab rock (a^2) * depth (h$)

$Mass= (ℓ)(a^2) (h)$ Mass= (ℓ)(a^2) (h)

Mass of the continent= (2940) (4700000) ^2 (28000)

                                    =$1.818 * 10^21 KG$

b)     $Kinetic energy= ½ MV^2 =½ * (1.818 * 10^21) (4 * 10^-2) ^2 =1.4544 * 10^18 J$ $Kinetic energy= ½ MV^2$ $Kinetic energy= ½ MV^2$

                         =$½ * (1.818 * 10^21) (4 * 10^-2) ^2$

= $½ * (1.818 * 10^21) (4 * 10^-2) ^2$

                           =$1.4544 * 10^18 J$  

c)     Speed of the jogger having the same kinetic energy as that of the continent

Hence K. E= 1.4544 * 10^18 J

Mass= $75kg$

$From the K. E=½ MV^2$

$V= √2 * 1.4544 * 10^18 J/75$

$V=7.638 *10^8$ $m/s$