A force is fully described by magnitude, direction and what?
A Temperature only
B Area only
C Line of action
D Color
Answer: C. Line of action. A force is a vector action with magnitude, direction, sense and point or line of application.
A free-body diagram shows a body and what?
A External forces
B Internal grain structure
C Temperature fields
D Material color
Answer: A. External forces. A free-body diagram isolates a body and displays applied forces, couples and support reactions.
Newton’s first law describes inertia when the resultant force is what?
A Zero
B Maximum
C Changing direction
D Always downward
Answer: A. Zero. With zero resultant force, a body remains at rest or in uniform straight-line motion.
Newton’s second law relates net force to mass and what?
A Displacement only
B Acceleration
C Temperature
D Pressure
Answer: B. Acceleration. The resultant force equals mass times acceleration for a particle of constant mass.
Newton’s third-law forces act on which bodies?
A The same point only
B One rigid body only
C Different bodies
D A single contact surface only
Answer: C. Different bodies. Action and reaction are equal and opposite but act on different interacting bodies.
The moment of a force about a point equals force times what distance?
A Path length
B Body mass
C Angle in degrees
D Perpendicular lever arm
Answer: D. Perpendicular lever arm. Moment magnitude is force times the perpendicular distance from the point to the force line.
A couple consists of equal opposite forces with what separation?
A Nonzero perpendicular spacing
B Zero distance
C Same line of action
D Unequal magnitudes
Answer: A. Nonzero perpendicular spacing. A couple produces a pure moment when equal opposite forces act along separated parallel lines.
Varignon’s theorem states that a resultant moment equals what?
A Product of all forces
B Sum of component moments
C Zero for every system
D Average support reaction
Answer: B. Sum of component moments. The moment of a force system’s resultant equals the sum of moments of its components.
In planar equilibrium, the sum of horizontal forces must be what?
A Equal to weight
B Positive
C Zero
D Equal to moment
Answer: C. Zero. Static planar equilibrium requires both force components and the net moment to vanish.
A pin support in a 2D model provides how many force reactions?
A Two
B One
C Three
D Zero
Answer: A. Two. A frictionless pin restrains translation in two directions but allows rotation.
A roller support in a 2D model typically provides how many reactions?
A Zero
B Two
C One
D Three
Answer: C. One. A smooth roller supplies one reaction normal to the supporting surface.
A fixed support in 2D resists force and what?
A Temperature
B Moment
C Density
D Electrical current
Answer: B. Moment. A fixed support restrains both translations and rotation, producing two force components and a moment.
An ideal truss member carries axial force and what assumption?
A Distributed bending loads
B Torsion only
C Fluid pressure
D Pin-jointed ends
Answer: D. Pin-jointed ends. Ideal truss members are straight, pin-connected and loaded at joints, so they carry axial force.
The method of joints applies equilibrium at what?
A Every member midpoint
B The support surface only
C The whole bridge span only
D Each truss joint
Answer: D. Each truss joint. At each joint, the connected member forces must satisfy force equilibrium.
A two-force member has forces that are equal, opposite and what?
A Perpendicular
B Unequal
C Non-coplanar always
D Collinear
Answer: D. Collinear. For equilibrium, the two end forces on a two-force member are collinear and opposite.
A centroid is the geometric centre of what?
A Mass density only
B Area or volume
C Applied force
D Support reaction
Answer: B. Area or volume. The centroid is the geometric centre of a line, area or volume.
For a homogeneous body in uniform gravity, its centre of gravity coincides with what?
A Centre of mass
B Elastic centre
C Shear centre
D Neutral axis always
Answer: A. Centre of mass. Uniform gravity makes the centre of gravity coincide with the centre of mass.
The second moment of area measures resistance to what?
A Translation only
B Bending deformation
C Temperature change
D Surface corrosion
Answer: B. Bending deformation. Area moment of inertia reflects how area is distributed about an axis and influences bending stiffness.
The parallel-axis theorem adds area times what?
A Distance squared
B Distance cubed
C Perimeter
D Radius only
Answer: A. Distance squared. For area moment of inertia, I = I-centroid + A d squared.
Limiting friction is proportional to normal force through what factor?
A Poisson ratio
B Elastic modulus
C Friction coefficient
D Thermal coefficient
Answer: C. Friction coefficient. At impending sliding, friction magnitude is mu times the normal reaction.
Friction on a contact surface opposes what tendency?
A Weight always
B Normal reaction
C Relative motion
D Applied moment always
Answer: C. Relative motion. Friction acts against relative sliding or its impending direction at the contact.
A cable supporting a load primarily carries what?
A Compression
B Bending only
C Shear only
D Tension
Answer: D. Tension. A flexible cable transmits tensile force along its length.
A planar concurrent force system has lines of action meeting at what?
A Two parallel axes
B A circle
C A centroid only
D One point
Answer: D. One point. Concurrent forces share a common point of intersection.
The resultant of perpendicular 3 N and 4 N forces has magnitude what?
A 1 N
B 5 N
C 7 N
D 12 N
Answer: B. 5 N. The orthogonal components form a 3-4-5 right triangle.
Static determinacy concerns whether reactions can be found using what?
A Equilibrium equations
B Material color
C Temperature data
D Traffic counts
Answer: A. Equilibrium equations. A statically determinate system has unknown reactions solvable from equilibrium alone.