Answer:
Because the mechanical advantage of the machine is affected by friction and weight but velocity ratio is not. So, mechanical advantage is less than velocity rate. Thus, the machine's efficiency is less than 100% and can't be a perfect machine
the action and reaction do not lead equilibrium if action and reaction force react on different objects
Convection currents occur in the magma drive plate tectonics. Here heat is generated from the radioactive decay of elements in the interior of the Earth, creating magma in the asthenosphere.
