For more Anna University Study Materials search here http www vidyarthiplus com search html 1 Define force www Vidyarthiplus com GE6253 ENGINEERING MECHANICS UNIT 1 BASICS STATICS OF PARTICLES 2 Differenciate between particles and rigid body VIDYARTHIPLUS Anna University Students Online Community Force is a physical quantity that changes or tires to change the state of rest or of uniform motion of an object Particle is a body which has mass but no dimension where as rigid body as both mass and dimensions Particle can have only translational motion where as rigid body can have translational as well as rotational motion www Vidyarthiplus com The rate of change of momentum of a body is directly proportional to the applied force and takes place in the direction of the force Everybody tries to be in it s state of rest or of uniform motion along a straight line unless it s acted upon by an external unbalanced force Every action has an equal and opposite reaction 4 State newton s second law of motion 5 State newton s third law of motion 3 State newton s first law of motion 1 For more Anna University Study Materials search here http www vidyarthiplus com search html For more Anna University Study Materials search here http www vidyarthiplus com search html 9 8 Define unit vector Define the following terms 6 State law of parallelogram of vectors A vector having magnitude one unit is known as a unit vector 7 State the principle of transmissibility of force with simple sketch According to principle of transmissibility of force the force can be transmitted from one point to another on it is line of action without causing by any change in the motion of the object EG force F can be transmitted from A to B If two vectors 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 www Vidyarthiplus com Collinear forces act along the same line where as concurrent forces have lines of action intersecting at one point b If lines of action of all forces intersected at a single point the forces are A system of coplanar concurrent forces can be reduced to a single force known as concurrent forces a If all forces act in one plane they are known as coplanar forces 10 Defferentiate between collinear and concurrent forces Define resultant of coplanar concurrent force system which is known as resultant force b concurrent forces a coplanar forces 11 2 For more Anna University Study Materials search here http www vidyarthiplus com search html For more Anna University Study Materials search here http www vidyarthiplus com search html 14 13 in equilibrium state triangle law of forces State parallelogram law of forces Resultant force makes the object move whereas equilibrant force keeps it 12 what is the difference between a resultant force and equilibrant force 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 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 www Vidyarthiplus com If three concurrent forces are in equilibrium magnitude of any force is proportional to the sine of angle between the other two forces ii The algebraic sum of vertical components of all forces acting the particle must be zero i The algebraic sum of horizontal components of all forces acting the particle must be zero State the necessary and sufficient condition for static equilibrium of a 16 particle in two dimensions For static equilibrium of a particle in two dimensions 17 State triangle law of equilibrium Statelami s theorem 15 3 For more Anna University Study Materials search here http www vidyarthiplus com search html For more Anna University Study Materials search here http www vidyarthiplus com search html 1 State varignon s theorem 18 What is a free body diagram UNIT 2 EQUILIBRIUM OF RIGID BODIES The algebraic sum of moments due to all forces acting on the object about any point is equal to the moment of their resultant about the same point A force system in a plane in which the lines of action all forces intersect at a single point is called coplanar concurrent force system If three forces acting on a particle are represented by the three sides of a triangle in magnitude and direction when taken in order the particle will remain in equilibrium www Vidyarthiplus com Moment represents the turning effect of a force where as couple consists of two equal and opposite forces separate by some distance moment of force various from point to point but moment of a couple is same about any point in the plane Couple moment is said to be a free vector as it can be transferred to any point in the plane without causing any change in its effect on the body Twonon collinear parallel forces having same magnitude but opposite direction from a couple 3 Why the couple moment is said to be a free vector 4 Distinguish between couple and moment 2 Define couple 4 For more Anna University Study Materials search here http www vidyarthiplus com search html For more Anna University Study Materials search here http www vidyarthiplus com search html 5 What is meant by force couple system 7 When is moment of force zero about a point 8 When is moment of force maximum about a point The moment of force about a point is zero its line of action passes through that point A coplanar non concurrent system with zero resultant force is not necessarily In equilibrium as it can have a non zero resultant moment 6 Can a coplanar non concurrent system with zero resultant force necessarily be in equilibrium A system of coplanar non concurrent force system acting in a rigid body can be replaced by a single resultant force and couple moment at a point known as force couple system www Vidyarthiplus com ii It is applied perpendicular to the line joining the point to the point of application of force Moment of force is maximum about a point when i Its applied at maximum result from the point and 9 When is moment of force zero about a line Moment of force about a line is zero when ii Line of action of force intersects that line i Force is parallel to that