Lami’s Theorem MCQs
1. Three coplanar forces A, B and C acting at a point in the plane are in equilibrium. If the given value of A is 1.9318 kg wt and sinθ1 is 0.9659, what is the value of C?
a) 1
b) 2
c) 0.9659
d) ½
Answer: (a) 1
2. If the body is under equilibrium under the influence of a set of non-colinear force, then the minimum number of forces has to be
a) Two
b)Three
c) Four
d) Five
Answer: (b) Three
3. What is the minimum number of non-zero vectors in different planes that can be added to give a resultant of zero?
a) Two
b) Three
c) Four
d) Five
Answer: (c) Four
4. According to Lami’s theorem which of the following statements is true?
a) Three forces acting at a point will be in equilibrium.
b) Three forces acting upon a particle will be in equilibrium if they are represented in magnitude and direction by the sides of a triangle, taken in order.
c) If three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two.
d) Three forces acting at a point can be represented by a triangle, each side being proportional to the force.
Answer: (c) If three forces acting at a point are in equilibrium, each force is proportional to the sine of the angle between the other two.
5. Which of the following theories states that “if a body is in equilibrium under the action of three coplanar and concurrent forces, each of the forces is proportional to the sine of the angle between the other two.”
a) Parallelogram Law of Forces
b) Lami’s Theorem
c) Triangle Law of Forces
d) Polygon Law of Forces
Answer: (b) Lami’s Theorem
6. Which of the following is true about Lami’s theorem?
a) The theorem is derived based on the cosine rule of trigonometry
b) The theorem is only applicable to regular shaped bodies in equilibrium
c) The theorem is helpful in determining the unknown forces acting at a point for an object in equilibrium.
d )The theorem determines the forces acting on a moving body.
Answer: (c) The theorem is helpful in determining the unknown forces acting at a point for an object in equilibrium.
