When we are in a stationary car that moves rapidly to gain speed,
we get pushed back against our seat.
And when brakes are applied, we get pushed ahead.
Or when we take a sharp right turn, we are pushed towards the left.
These are all situations where we are Accelerating!
We have all experienced this whether in a car,
or a bus, or while riding a motorbike.
Simply put, when velocity changes, we have acceleration.
I still haven't defined what acceleration is.
I just told you that when velocity changes, there will be acceleration.
Okay, let me give you two examples.
In the first one,
a car is traveling in a straight line at a constant speed of 80 kilometers an hour.
And in the second one,
a plane is traveling in a straight line at a constant speed
of 1,000 kilometers an hour.
In which case do you think Acceleration is involved?
None! In both cases, the velocity is not changing at all.
Hence, there will be no acceleration in either of the cases!
Most people relate acceleration to high speed !
And that's clearly not true!
Acceleration will only exist when there is change in velocity.
Do you remember what velocity is ?
Its speed with direction and its hence of vector quantity!
Why is this important?
Let's say a body moves from rest and
reaches a velocity of 20 kilometers an hour in five seconds.
Will acceleration be involved here?
Yes, because the velocity is changing. It was zero initially,
and at the end of five seconds it's 20 kilometers per hour.
In another scenario,
assume that a body is moving at 30 kilometers an hour,
and then it moves right at 30 kilometers an hour
and continues traveling at the same speed of 30 kilometers per hour.
Will there be acceleration in this case?
The answer is yes !
As the direction is changing,
the velocity will also change.
The only thing constant in this example is speed.
But the velocity changes as the direction changes!
So this was the most important concept you had to know about acceleration.
It will exist only when there is a change in velocity!
But how is acceleration calculated?
Acceleration is defined as the rate of change of velocity.
In terms of a formula,
Acceleration can be written as 'change in velocity'
'over the time taken'. If the velocity of an object changes
from an initial value of U to the final value of V, in time t, then the acceleration
"a" can be written as 'V minus U' over t.
Said this object is at rest initially at point "a".
It then travels to the right and attains the velocity of
'10 meters per second' in five seconds.
What will be the acceleration here at point B?
We can look at the formula to get the answer!
The initial velocity U is zero meters per second as the object is stationary.
The final Velocity V is 10 meters per second.
And the time taken t is 5 seconds.
Hence the acceleration a will equal '10 meters per second' minus
'zero meters per second', divided by 5 seconds.
So this will equal 10 meters per second divided by 5 seconds.
'10 divided by 5' is 2.
Wait.. hold on..
What will be the units of acceleration?
We should get a hint by looking at this.
The units of acceleration will be
'meters per second' per second.
Because it's the change in velocity over the time taken!
As this is meters per second,
we can carry this second to the denominator
and what we will get is 'meters per second squared.'
This one is more intuitive, but this one is a bit neater I would say.
So the acceleration in this case will be '2 meters per second squared'.
And acceleration is also a vector quantity!
Here,
Acceleration and Velocity are in the same direction!
There are many more important concepts
about acceleration, which we will cover in the coming videos.
