L1 - Introduction to Motion - Motion, Class 9 Science Video Lecture

I
you
one dimensional motion as we look at our
surroundings we will find many objects
at motion and many interest in a real
sense motion and the state of being
addressed our profound topics let's try
to have a better understanding of these
subjects consider a man sitting in a
park as a squirrel runs by him
the man is addressed with respect to his
surroundings the squirrel is in motion
with respect to the man now consider the
earth and the moon with respect to the
moon the earth is in motion and so the
man is also moving here the moon is a
frame of reference therefore an object
is said to be in motion if there is a
change in the position of the object
with respect to the frame of reference
so far we've discussed motion and frame
of reference
let's now understanding the meaning of
distance and displacement
a bus moves from destination a
destination beep in its course it
changes its direction constantly and
reaches destination B in the process the
bus has covered a distance of 2,000
meters the length of the path covered is
called distance D traveled here the
moving body has only magnitude no
direction and hence distance is a scalar
quantity now let us consider that there
is an alternate route which takes the
bus to the destination B in the shortest
distance that is a thousand five hundred
meters the straight distance between the
initial and the final positions of a
moving body in a particular direction is
called its displacement here the moving
body has magnitude in direction hence
displacement is a vector quantity let's
now discuss speed and velocity speed is
the distance traveled by a body in unit
time consider an object moving from
destination a to destination B at a
certain time T that is 600 seconds the
distance D between the point is 2,000
meters let's calculate the object's
speed speed is equal to distance D by
time T 2000 by 600 is three point three
the SI unit of speed is meter per second
this is represented by the symbol M s to
the power of minus 1 or M / S when we
calculate the displacement of the object
between the same points per unit time we
will obtain its velocity that is
velocity is the rate of change of
displacement so velocity V is equal to
displacement by time
that is thousand five hundred by four
hundred is equal to 3.75 the SI unit of
velocity and speed is meter per second
what happens when a body moving in a
certain direction changes its speed
suddenly let's consider two vehicles
moving in parallel with uniform velocity
that is 10 meters per second from point
A to point B suddenly one vehicle
increases its velocity that is 15 meters
per second in three seconds and speeds
off towards point B as the velocity of
the vehicle has increased it is said to
have accelerated acceleration is
calculated as the rate of change of
velocity that is acceleration a is equal
to change in velocity by time here
change in velocity is 15 meters per
second minus 10 meters per second which
is 5 meters per second T is equal to 3
seconds therefore acceleration a is
equal to 5 by 3 which is 1.6 meters by
second square things to remember motion
is the change in position of an object
with respect to a frame of reference the
length of the path travelled by a moving
object is called distance distance is a
scalar quantity
displacement is the distance traveled by
an object with a certain magnitude
displacement is a vector quantity speed
is a distance traveled by a body in unit
time and velocity is the rate of change
of displacement the SI unit of velocity
and speed is meter per second
acceleration is calculated as a rate of
change of velocity the SI unit of
acceleration is meters by second square
you