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 4700km on a side and 37km deep and that the rock has an average mass density of 2720kg/m^3. the continent is moving at the rate of about 4.6cm/year. a) what is the mass of the continent. b) what is the kinetic energy of the continent?

A) We need to first determine the volume of the continent and then mass would be = Volume x density

Volume = 4.7 x 10^6 m x 4.7 x 10^6 m x 37 x 10^3m

= 817 x 10^15 cubic meter

Mass = V x density

= 817 x 10^15 cubic meter x 2720kg/m^3

= 2.2 x 10^21 Kg

B)

Kinetic Energy = ½mV²

= ½ x 2.2 x 10^21 Kg x ( 4.6cm/year. x 1m/100cm x 1yr/365.24day x 1day/24hr x 1hr/3600s)²

= 2340 J

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

pretty sure it's false