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# What is the Motion of a Body

MOTION

When a body changes its position continuously with respect to a stationery object, which is taken as a reference point. It can be depicted by this graph:

Motion includes both distance and displacement.

Distance is a scalar quantity because it has magnitude only.

Displacement is a vector quantity because it has both magnitude and direction.

TYPES OF MOTION

There are 2 types of motion:

1. UNIFORM MOTION

An object shows uniform motion if it travels equal distance in equal interval of time. It can be depicted by this graph:

1. NON UNIFORM MOTION

An object is said to be in non uniform motion if it covers unequal distance in equal interval of time. It can be depicted as:

NOTE: The motion of freely falling body is an example of non-uniform motion. Non-uniform motion is also known as accelerated motion.

SPEED

Speed of a body is the distance travelled by it in per unit time.

The formula to calculate is: Speed (v) = Distance (s) / Time(t)

S.I. Unit for speed = metre/sec or m/s

Speed is a scalar quantity.

VELOCITY

Velocity of a body is the distance travelled by it in per unit time in given direction. It can also be defined as speed in a specific direction.

It can be calculated as:

V = s / t

Where, v is the velocity, s is the distance and t is the time.

Velocity is a vector quantity.

If 2 types of velocity are given in the question as initial and final velocity, then average velocity is calculated as-

Average velocity= Initial velocity + Final velocity/2

ACCELERATION

Acceleration is the change in velocity of a moving body with time. It can be calculated as:

Acceleration= Change in velocity/ Time taken

Or, A= v-u/t

Where, v= final velocity, u= initial velocity and t= time

S.I. unit= ms-2

Acceleration is a vector quantity and when a body is moving with a uniform velocity, its acceleration will be zero

It is of 2 types:

1.UNIFORM ACCELERATION

When acceleration increases at equal amount in equal amount of time, it is known as uniform acceleration.

2.NON UNIFORM ACCELERATION

When acceleration increases at unequal amount in equal amount of time, it is known as non uniform acceleration.

Q.1. Motion includes:
a. Distance
b. Displacement
c. Both
d. None

Ans. c

Q.2. What is the SI unit of speed:
a. cm sec-1
b. met sec-1
c. km sec-1
d. met min-1

Ans. b

Q.3. What is the formula to calculate the speed:
a. v= s/t
b. v= t/s
c. s= s/t
d. s=t/s

Ans. a

Q.4. A train has covered 2000metres in a minute. Calculate the speed.
a. 33.33 m/s
b. 33.43 m/s
c. 50 m/s
d. 34.43 m/s

Q.5. Speed is a:
a. scalar quantity
b. vector quantity
c. mixed quantity
d. None

Q.6. Velocity is a:
a. scalar quantity
b. vector quantity
c. mixed quantity
d. None

Ans. a

Q.7. If a train was moving with a initial velocity of 50 m/s and final velocity of 85 m/s. Calculate the average velocity of the train.
a. 67.5 m/s
b. 77.5 m/s
c. 50 m/s
d. 67 m.s 