What is meant by concurrent forces?
A
Forces acting on different bodies
B
Forces that do not intersect
C
Forces whose lines of action intersect at a point
D
Forces acting in opposite directions
Analysis & Theory
Concurrent forces are forces whose lines of action intersect at a common point.
What is the resultant of two concurrent forces F1 and F2 at angle θ?
B
√(F1² + F2² + 2F1F2cosθ)
Analysis & Theory
The resultant is given by vector addition using the law of cosines: R = √(F1² + F2² + 2F1F2cosθ).
Which rule is used to find the direction of the resultant force between two concurrent forces?
Analysis & Theory
The sine rule helps to find angles in vector triangles formed by concurrent forces.
What is the condition for equilibrium of concurrent coplanar forces?
A
Forces must be perpendicular
B
Resultant must be maximum
D
Forces must be parallel
Analysis & Theory
For equilibrium, the vector sum (resultant) of all concurrent coplanar forces must be zero.
Which law is used to determine the resultant of two forces acting at an angle?
Analysis & Theory
The parallelogram law of forces is used when two forces act at a point at an angle.
What is a couple in mechanics?
A
Two equal and opposite parallel forces not in the same line
B
A pair of concurrent forces
D
Two forces acting at the same point
Analysis & Theory
A couple is formed by two equal and opposite forces whose lines of action do not coincide.
What effect does a couple have on a body?
Analysis & Theory
A couple causes rotation without translation.
What is the net force of a couple?
B
Equal to one of the forces
C
Maximum of the two forces
D
Product of the two forces
Analysis & Theory
The net (resultant) force of a couple is always zero, but it produces a moment.
What is the moment of a couple?
B
Product of force and perpendicular distance
Analysis & Theory
Moment of a couple = Force × Perpendicular distance between the forces.
In what direction does the moment of a couple act?
A
Along the line of force
B
Along the perpendicular distance
C
Along the axis of rotation
Analysis & Theory
The moment acts perpendicular to the plane of the couple, i.e., along the axis of rotation.
Which of the following is true about a couple?
B
Does not produce torque
C
Can be balanced by a single force
D
Can only be balanced by an equal and opposite couple
Analysis & Theory
A couple can only be balanced by another couple of equal magnitude and opposite direction.
If two forces 10 N each form a couple with a 0.5 m separation, what is the moment?
Analysis & Theory
Moment = Force × Distance = 10 × 0.5 × 2 = 10 Nm (since both forces contribute to rotation).
Can a couple be in equilibrium?
A
Yes, if the forces are unequal
B
No, couples always rotate bodies
C
Yes, if an opposite couple is applied
D
Only if one force is removed
Analysis & Theory
A couple can be in equilibrium if an equal and opposite couple is applied to cancel its effect.
Which method is used to find resultant of multiple coplanar concurrent forces?
Analysis & Theory
Resultant of multiple concurrent forces is found using vector addition considering magnitude and direction.
Which instrument is used to experimentally determine force directions in a plane?
Analysis & Theory
A force table is used to study equilibrium and the composition of coplanar forces.
The condition for equilibrium of a body under three concurrent forces is given by:
B
All forces point in the same direction
C
Forces form a closed triangle
Analysis & Theory
If a body is in equilibrium under three concurrent forces, they form a closed triangle vectorially.
A system of concurrent forces acting at a point in the same plane is known as:
Analysis & Theory
Forces lying in the same plane and meeting at a point are called concurrent coplanar forces.
Which of the following is not a vector quantity?
Analysis & Theory
Pressure is a scalar quantity; force, torque, and couple are vector quantities.
If two equal forces act at 60° angle, the resultant will be:
B
Equal to one of the forces
Analysis & Theory
Resultant of two equal forces at angle θ is less than their sum unless θ = 0°.
Which of the following results in a couple?
B
Two forces acting at a point
C
Two equal and opposite parallel forces
Analysis & Theory
A couple is formed by two equal and opposite forces acting along parallel lines.
The unit of moment of a couple is:
Analysis & Theory
Moment (or torque) is measured in Newton-meter (Nm).
In equilibrium, the algebraic sum of moments about any point is:
Analysis & Theory
For equilibrium, the sum of clockwise and anticlockwise moments must be zero.
If resultant of forces is zero, the body is in:
Analysis & Theory
Zero net force implies equilibrium, where the body is either at rest or moving at constant velocity.
What is the equilibrant of a system of forces?
A
Force that supports motion
B
Force that cancels the resultant
C
Force equal to the net moment
Analysis & Theory
Equilibrant is the force equal in magnitude and opposite in direction to the resultant.
A force of 5 N is resolved into components at 60°, the vertical component is:
Analysis & Theory
Vertical component = 5 × sin(60°) ≈ 4.33 N.
The magnitude of a couple depends on:
C
Only the angle between forces
D
Both force and perpendicular distance
Analysis & Theory
Magnitude of a couple = Force × Perpendicular distance between lines of action.
Two forces of 10 N each form a couple. What should be their separation to produce a moment of 20 Nm?
Analysis & Theory
Moment = Force × Distance × 2 ⇒ 10 × d × 2 = 20 ⇒ d = 1 m.
Which is not a method for finding resultant of concurrent coplanar forces?
A
Graphical vector addition
Analysis & Theory
Centrifugal method is not used for force resolution or resultant calculation.