ASVAB Practice Test

A perpetual-motion machine can never be built because it is not possible to eliminate what?

1. Clasticity

2. Elasticity

3. Friction

4. Gravity

The correct answer is: Clasticity

A perpetual-motion machine is a hypothetical device that operates indefinitely without an external energy source. The concept directly contradicts the laws of thermodynamics, particularly the first and second laws, which state that energy cannot be created or destroyed and that systems tend to move toward greater entropy. The reason why the correct answer relates to clasticity involves the fundamental understanding of mechanical energy losses in systems. Clasticity refers to the tendency of materials to revert to their original shape after deformation. Although all physical systems exhibit some level of elasticity, it is the energy lost in deformation through clastic behavior, along with other factors such as friction, that ultimately prevents a machine from being able to run perpetually. In practical terms, real machines experience energy losses due to friction in moving parts and heat dissipation. As a result, even the most efficiently designed machine will eventually run out of energy due to these unavoidable losses. Therefore, the nature of materials, including clastic properties, contributes to energy dissipation in a way that makes a perpetual-motion machine impossible. The options about friction and gravity also connect to energy losses and constraints on motion but do not focus on the mechanical properties of materials in the same way. Thus, clasticity stands as a fundamental reason for energy