Infinity Science study: Physical Quantities !!! Definition and Unit !!! Scalar, Vector, Displacement, Velocity and Acceleration.

PHYSICAL QUANTITIES

SCALAR QUANTITIES:

• Physical quantity which have magnitude only and no direction are called Scalar Quantities.

          Example:- Mass, Speed, Volume, Work, Time, Power, Energy etc.

VECTOR QUANTITIES:

• Physical quantity which have magnitude and direction both and witch obey the triangle law are called vector quantities.

          Example:- Displacement, Acceleration, Velocity, Force, Momentum, Torque etc.

KINEMATICS

• It is branch of mechanics, which deals with the motion of object.

DISTANCE:

• The length of the actual path covered by a body in a particular time interval is called distance. It always positive.
• It is a scalar quantity which has magnitude only. Its unit is also Metre.

DISPLACEMENT:

• The difference between the final and the initial position of an object is called Displacement. It may be positive, negative or zero.
• It is a Vector quantity. Its unit is Metre.
• The magnitude of displacement may or may not be equal to the path length travelled by an object.                                                                                                                                                                                              Displacement ≤ Distance

SPEED:

• Speed is the distance covered by a moving body in unit time. Its unit is m/s.
• It is a Scalar quantity. It is always equal to or greater than magnitude of the velocity.
• The average speed of a particle for a given interval of time is defined as the ratio of total distance travelled to the total time taken.

                        Average Speed = Total distance travelled / Total time taken

• If a body covers first half distance with speed v₁ and the next half with the speed v₂ then

                                   Average Speed = 2v₁v₂ / v₁+v₂

VELOCITY:

• The rate of change of Displacement of a body is called velocity. Its unit is Metre/Second (m/s).

                                             Velocity = Displacement / Time

• Velocity is Scalar quantity. It may be positive or Negative.

                                    Average velocity = Total displacement / Total time

• If a body covers first half distance with velocity v₁ and the next half with the velocity v₂ then

                                   Average Velocity = 2v₁v₂ / v₁+v₂

• If a body travels with uniform velocity v₁ for time t₁ and with the uniform velocity v₂ for time t₂, then

                                 Average Velocity = v₁t₁ + v₂t₂ / t₁ + t₂

• If a body is moving on a circular path, then after completing one complete cycle, its average velocity of is zero.

UNIFORM VELOCITY:

• An object is said to be moving with uniform velocity if it undergoes equal displacements in equal time intervals of time.

NON-UNIFORM VELOCITY:

• An object is said to be moving with non-uniform velocity if it undergoes unequal displacements in equal time intervals of time.

RELATIVE VELOCITY:

• When two bodies are moving in the straight line, the speed (or velocity) of one with respect to  another is known as its  relative speed (or velocity).

ACCELERATION:

• It is the rate of change of velocity. Its unit is Metre / Second Square (m/s²). It is a Vector quantity.
• When the velocity of a body increases with time then its acceleration is positive and if velocity decreases with time then its acceleration is negative and it’s called Retardation or Deacceleration.
• Acceleration of an object is zero. If it is at rest or moving with the uniform velocity.