 # Newton's Second Law of Motion

## (5) Newton's second law of motion

• Newton's first law of motion qualitatively defines the concept of force and the principle of inertia
• For an body at rest, application of force causes a changed in its existing state and application of force on a body moving with uniform velocity would give the body under consideration as acceleration
• Newton's second law of motion is a relation between force and acceleration
• Newton's second law of motion says that
" The net force on a body is equal to the product of mass and acceleration of the body"
Mathematically
Fnet=ma                               (1)
Where Fnet is the vector sum of all the forces acting on the body
• Above equation -(1) can be resolved along x,y and z components .Thus in component form
Fnetx=max
Fnety=may
Fnetz=maz
• Component of acceleration along a given axis is caused only by the net component of force along that axis only not by the components of force along other axis
• Newton's second law of motion is completely consistent with newton first law of motion as from equation (1) F=0 implies that a=0
• For a body moving under the influence of force, acceleration at any instant is determined by the force at that instant not by the previous motion of the particle
• Newton's second law of motion is strictly applicable to a single particle .In case of rigid bodies or system of particles, it refers to total external forces acting on the system excluding the internal forces in the system.