Force Analysis MCQs – Part 1

Practice SSC JE and other civil engineering exam questions on force analysis: types of supports and their reactions, constraints, concurrent and parallel force systems, stability and proper constraint of planar bodies, equations of static equilibrium, static loads and simple harmonic motion. Tap an option to check it, then open the full explanation for each question.

Question 1Easy

If we use a link support in a structural system, how many unknowns would we have?

Full explanation

Answer: B. 1

A link can only push or pull along its own length, so it gives one unknown reaction.

Question 2Easy

Gradually applied static loads do not change with time their:

Full explanation

Answer: D. All options are correct

A static load, once fully applied, keeps the same magnitude, direction and point of application.

Question 3Medium

If all the reactions acting on a planar system are concurrent, then the system is:

Full explanation

Answer: C. Essentially unstable

Concurrent reactions all pass through one point, so they cannot resist a moment about that point. The body is unstable.

Question 4Easy

By applying the static equations ΣH = 0, ΣV = 0 and ΣM = 0 to a determinate structure, we may determine:

Full explanation

Answer: D. All options are correct

In a statically determinate structure, the three equations give the reactions, and from them the shear force and bending moment anywhere.

Question 5Easy

How many constraints are there in a free-rotation support used in a planar system?

Full explanation

Answer: B. 2

A free-rotation (hinge/pin) support stops horizontal and vertical movement but allows rotation: 2 constraints.

Question 6Medium

If in a planar system only 2 reaction forces are acting, then the system is:

Full explanation

Answer: A. Essentially unstable

A planar body needs at least 3 suitable reactions. With only 2 it cannot satisfy all three equilibrium equations under general loading, so it is essentially unstable. (The revised official key accepted (c); see the note.)

Question 7Medium

How many of the following cases are improperly constrained? 1. Parallel forces 2. Concurrent forces 3. Perpendicular forces 4. Only moment

Full explanation

Answer: B. 2

Reactions that are all parallel, or all concurrent, make a body improperly constrained: 2 cases.

Question 8Medium

If a system has more equations of equilibrium than the number of forces (reactions), then the system is:

Full explanation

Answer: B. Partially constrained

Fewer reactions than equations means the body is partially constrained (and unstable).

Question 9Easy

A body is said to move with simple harmonic motion if its acceleration is:

Full explanation

Answer: C. proportional to the distance from the point of reference and directed towards it

In SHM, a = −ω²x: proportional to the displacement and always directed towards the mean position.

Question 10Easy

If the lines of action of the forces in a system meet at a point, these forces are called:

Full explanation

Answer: C. Concurrent forces

Forces whose lines of action pass through one common point are concurrent forces.

Question 11Easy

How many constraints are there in a fixed support in a planar system?

Full explanation

Answer: B. 3

A planar fixed support stops horizontal movement, vertical movement and rotation: 3 constraints (Rx, Ry, M).