Two Marks Questions with Answers

Two Marks Questions with Answers

Q.1

Define resultant of coplanar concurrent force system.

Ans. 

A system of coplanar concurrent forces can be reduced to ingle force which is known as resultant force.

Q.2

State the principle of physical independence of forces.

Ans. 

According to the principle of physical independence of forces, every force produces its own effect on the object independent of the other forces.

Q.3 

State superposition principle.

Ans. 

If more than one force act on an object, the combined effect due to all the forces is the vector addition of all the individual effects.

Q.4

What is the difference between a resultant force and equilibrant force? 

Ans. 

Resultant force makes the object move whereas equilibrant force keeps it in equilibrium. Both have same magnitude but opposite direction.

Q.5 

State triangle law of forces.

Ans. 

If two forces are represented in magnitude and direction by two sides of a triangle taken in order, their resultant is represented in magnitude and direction by the third side of the triangle drawn from starting point of first force to end point of the second force.

Q.6

State parallelogram law of forces.

Ans. 

If two forces are represented in magnitude and direction by two adjacent sides of a parallelogram, their resultant is represented in magnitude and direction by the diagonal of the parallelogram drawn from the common point.

Q.7 

State Lami's theorem.

Ans. 

If three concurrent forces are in equilibrium, magnitude of any force is proportional to the sine of angle between the other two forces.

Q.8

State the necessary and sufficient conditions for static equilibrium of a particle in two dimensions. 

Ans. 

For static equilibrium of a particle in two dimensions,

i) The algebraic sum of horizontal components of all forces acting on the particle must he zero.

ii) The algebraic sum of vertical components of all forces acting on the particle must be zero.

Q.9

State triangle law of equilibrium.

Ans. 

If three forces acting on a particle are represented by three sides of a triangle in magnitude and direction when taken in order, the particle will remain in equilibrium. 

Q.10

What is a free body diagram?

Ans. 

A force system, in a plane, in which the lines of action of all forces intersect at a single point is called coplanar concurrent force system.

Q.11 

State the relation between the three direction cosines.

Ans. 

cos2 θx + cos2 θy + cos2 θz  = 1

Q.12

Write a force of magnitude F as a vector in terms of if it is directed from A(x1, y1, z1) to B(x2, y2, z2)

Ans. 

Q.13

How will you find the direction cosine in the Z-direction of the resultant force of a concurrent spatial force system?

Ans. 

The direction cosine in z-direction is found using

Q.14

What are the minimum requirements for equilibrium of a particle in space? 

Ans. 

For an object to be in equilibrium it must be experiencing no acceleration. This means that both the net force and the net torque on the object must be zero.

Q.15 

How free body diagram is constructed?

Ans. 

It is the isolated diagram of an object/system of objects/any point in the system in which all forces and couple moments acting on it are shown including support reactions.

• When objects are supported by some supporting mechanisms, the supporting mechanism exerts a force or couple moment on the object which tries to restrict the motion of the object.

• These forces or couple moments which oppose or restrict the motion by objects are called support reactions.

Q.16

Sketch the free body diagrams for the cylinder B shown in Fig. 2.13.1.

Ans. 

Q.17

Resolve the 100 N force acting 30° to horizontal into two component one along horizontal and other along 120° to horizontal.

Ans. 

The 100 N force and its two components F1 and F2 are shown in Fig. 2.13.2.

The 100 N force is resultant of F1 and F2.

Q.18

Two forces of 400 N and 600 N act at an angle 60° to each other. Determine the resultant in magnitude and direction.

Ans. 

Let P = 400 N, Q = 600 N, α = 60°

By parallelogram law,

Q.19

State the concept of equilibrium of connected bodies. 

Ans. 

 (Refer section 2.11.1)