1. A particle has only mass and no size, while a rigid body maintains the relative positions of its particles when acted on by forces. 2. The resultant force on a particle is a single force that can replace multiple acting forces and produce the same effect. 3. For a particle to be in equilibrium, the sum of the horizontal forces and sum of the vertical forces must both be zero. 4. Newton's gravitational law states that the force between two masses is directly proportional to the product of the masses and inversely proportional to the square of the distance between them.

1. Unit I Statics of Particles
1. Define particle and rigid body.
Particle: It may be defined as an object which has only mass and no size.
Rigid body: A body said to be rigid, if the relative positions of any two particles in it donot change
under the action of the forces.
2. What is resultant force?
If a number of forces acting on a particle simultaneously are replaced by a single force ,
which could be produce the same effect as produced by the given forces that single force is called
Resultant force.
3. What are the minimum requirements for equilibrium of a particle?
1. Summation of all the horizontal forces is zero. (ΣH=0)
2. Summation of all the vertical forces is zero. (ΣV=0).
4. Define Newton`s Gravitational law.
It states that two particles of mass M and m are mutually attracts with equal and opposite
force F and –F of magnitude F is given by the formula,
F= G (Mm/r2)
ie., Force is directly proportional to the product of the two particles and inversely proportional to
the square of the distance of the two particles.
5. What is Lami`s theorem?
“If three forces acting on a particle are in equilibrium then each force is proportional to
the sine of the angle between the other two forces”
Mathematically written as,
𝐹1
𝑆𝑖𝑛𝜃1⁄ = 𝐹2
𝑆𝑖𝑛𝜃2⁄ = 𝐹3
𝑆𝑖𝑛𝜃3⁄
6. Define parallelogram law of forces.
It states that two forces acting on a particle may be replaced by a single force called their
resultant, obtained by drawing the diagonal of the parallelogram which has sides equal to the given
forces.
7. What is Principle of transmissibility?
It states that the conditions of equilibrium or of motion of a rigid body will remain
unchanged if a forces acting at a given point of the rigid body is replaced by a force of the same
magnitude and same direction but acting at a different point, provided that the two forces have the
same line of action.

2. 8. List out characteristics of force.
* Magnitude *Point of application * Line of action and direction.
9. What are the classification of system of forces?
1. Coplanar forces. (Forces acting on a plane)
* Concurrent forces
*Non-concurrent forces.
* Collinear forces.
* Parallel force.
*Non-Parallel forces.
2. Non-Coplanar forces. (Forces acting in
space)
* Concurrent forces
*Non-concurrent forces.
* Parallel force.
*Non-Parallel forces.
8. Define unit vector.
The vector having a unit length or unit magnitude is known as unit vector.
ie., unit vector=(vector quantity(F )/magnitude of (F))
10. Two forces 30 N and 40 N act at a point `O`. The included angle between them is 600. Find the
magnitude and the direction of the resultant.
11. Determine the resultant of the three concurrent forces F1=2i+ 3j -2.5k,F2=-i+5j-3k, and F3=7i-
7j=6k. Three forces are in Newton.
12. A vector F starts at point (2,-1, 2) and passes through the point (-1, 3, 5). Find its unit vector.
13. A vector F starts at point (2, -1, 2) and passes through the point (-1, 3, 5). Find its unit
vector.
14.A force of magnitude 750N is directed along AB where A is (0.8, 0, and 1.2) and B is (1.4,
1.2, and 0). Write the vector form of the force.
15.A forceF=8.25i+12.75j-18k) N acts throughtheorigin. Whatis the magnitude ofthis force
and angles it makes with x, y and z axes?
16.The line of action of 100N force F passes through the points A (2, 5, 8) and B (7, 2, 6). The
direction of the force is from A to B. Express F in terms of the unit vectors.
17. State triangle law of forces.
It states that “If two forces acting on a particle that can be represented by the two sides of
a triangle in the magnitude and direction taken one after another, then the side that closes the
triangle represents the resultant in opposite direction”.