Answer:
Element Is The Answer I think
the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from the formation of the Earth.
A pair of scissors .....................................
The block on the action of two forces, the Force of Friction and the Tangential Weight. Using the Newton's Secound Law, we have:
Using the Velocity Hourly Equation, we get:
Uniting the equations:
Entering the unknowns:

Obs: Approximate results
If you notice any mistake in my english, please let me know, because i am not native.