Question

A Piston will remain in equilibrium if ________

(a) Inertia force is applied in the same direction to the resultant force

(b) Inertia force is applied in the direction opposite to the resultant force

(c) Inertia force is applied in the direction Perpendicular to the resultant force

(d) Inertia force is applied in the direction Parallel to the resultant force

This question was addressed to me during an interview for a job.

Asked question is from Klien’s Construction topic in portion Inertia Forces in Reciprocating Parts of Machine Dynamics

Answer 1

Right answer is (b) Inertia force is applied in the direction opposite to the resultant force

To elaborate: Inertia force is an imaginary force which tends to act in the direction opposite to the resultant force to bring the body in equilibrium. The magnitude of this force is equal to that of resultant force.