Definition of Plane Motion and Rectilinear Motion Notes pdf ppt

Plane Motion:

If all moment of a particle occurs in a plane, it is called plane motion of the particle.

General Planar Motion:

General planar motion allows for simultaneous rotational and translational motion in a 2-D plane. The motion of the rigid body may be described as a simple superposition of the body’s translation and rotation as illustrated in the following figure.

Rectilinear Motion:

If the path of the motion of a particle is a straight line, it is called ‘Rectilinear motion.

Rectilinear motion is another name for straight-line motion. This type of motion describes the movement of a particle or a body.

A body is said to experience rectilinear motion if any two particles of the body travel the same distance along two parallel straight lines. The figures below illustrate rectilinear motion for a particle and body.

Rectilinear motion for a particle:

Rectilinear motion for a body:

Expression for Rectilinear Motion:



Above Fig. shows the movement of a particle r moving along a straight line. O’ is the initial position of Pat t = 0 and S =S0.

P is the position at time t and P’ is the position at time t+ ∆t

Displacement in time                         ∆t =∆S

Displacement m unit time =∆S /∆t


∆S /∆t =v av [Average Velocity].

In the limiting case as ∆t à 0, we have

v = Lt .∆S /∆t= dS /dt ,

where v is called instantaneous velocity.

v = dS/dt =S

v = v o ­at t =0 (i.e., at initial point 0,

The average acceleration during ∆t is defined as

a av =∆v / ∆t.

In  the limiting case

where a is called the instantaneous acceleration of the particle.

a = dv /dt =v


-a is called instantaneous deceleration or retardation

Thus ,              a d2S / dt = S

From (1.1)                               dt = dS /v

and from (1.2) we have

dt = dv / a.

thus ,      dt = dS /v = dv /a

                         v dv =a dS

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