Question

Which of the following statements of D’Alembert’s principle are correct?

1. The net external force F actually acting on the body and the inertia force F₁ together keep the body in a state of fictitious equilibrium.

2. The equation of motion may be written as F + (-ma) = 0 and the fictitious force (-ma) is called an inertia force.

3. It tends to give solution of a static problem an appearance akin to that of a dynamic problem.
1. 1 and 3 only
2. 1 and 2 only
3. 2 and 3 only
4. 1, 2 and 3

Answer 1

Correct Answer - Option 2 : 1 and 2 only

Explanation:

D’Alembert’s principle involves

1. D'Alembert's principle of virtual work states that a system of rigid bodies is in dynamic equilibrium when the virtual work of the sum of the applied forces and the inertial forces is zero for any virtual displacement of the system.

Equation of motion is given by:

F = ma

It can be rearranged as:

F+ (-ma) = 0 (As per D’Alembert’s principle)

where (-ma) is the inertia force and F is an external force.

1. It tends to give the solution procedure of a dynamic problem an appearance akin to that of a static problem.