**2(c) state what is meant by uniform acceleration and calculate the value of an acceleration using change in velocity/time taken**

**2(d) discuss non-uniform acceleration.**

**Acceleration**.

Acceleration is the

**rate of change of velocity**. Its formula is

**change in velocity (final velocity minus initial velocity) /time taken**. From the formula, we can deduce its SI unit. By dividing m/s by seconds we get

**m/s square**or

**m/s^2**, which is the SI unit of acceleration.

Now I'll go into a bit more detail .By rate of change of velocity, it means by how much the velocity of an object is increasing or decreasing in one second. E-g if the acceleration of a car is 4 m/s square, it means that the velocity of that body is increasing by 4 m/s every second. So if the car was initially at rest, and it accelerated at 4m/s^2 for four seconds, its velocity after 4s would be 16m/s. As it is derived from velocity, acceleration is a vector quantity too.

A car is moving at a velocity 20m/s. The driver presses the accelerator and the car reaches a velocity of 80m/s in the next 20s . Calculate the acceleration in these 20s .

Solution:

Our first task would be to get the change in velocity. The change in velocity would be final velocity minus initial velocity, that is 80 minus 20. This is because the car was already traveling at a velocity of 20m/s, and we want the change of velocity only. We already have the time, which is 20s. So the acceleration of the car would be 80-20/20 = 3m/s^2. This means that for 20s, the velocity of the car increased by 3m/s every one second.

**Deceleration.**

Lets see, what if the velocity of the car had decreased instead of increasing. Lets say that the car was traveling at a velocity of 80m/s and the driver applied breaks and after 20s, the velocity of the car was 20m/s. In this case, the car would be actually decelerating, which is the opposite of acceleration. We would first take the change in velocity by subtracting the initial velocity from the final one. It would be 20-80, that is -60 m/s. Divide it by time, and the answer would be -3m/s^2. So, the velocity of the car is actually decreasing by 3m/s every second, and it would be called deceleration, not acceleration.

## Remember

If there is no increase or decrease in the velocity of an object, it means that the acceleration of that object is zero. This is so because acceleration is the rate of change of velocity, and if there is no change in velocity, the acceleration is zero.

## Uniform and a Non uniform acceleration.

#### Uniform acceleration

Uniform acceleration means that the acceleration of the car remains the same over a period of time. It means that the acceleration is constant, and neither increasing nor decreasing. Always remember that in uniform acceleration, the velocity of the object increases at a uniform rate too.

(uniform acceleration)

#### Non uniform acceleration

The diagram above shows two graphs of non uniform acceleration one is of Decreasing and other of increasing acceleration. Non uniform acceleration means that the acceleration of an object is not constant, but either increasing or decreasing over a passage of time, as shown in the diagram above.

REMEMBER: A graph representing a non uniform acceleration can be of any type except like the graph of uniform acceleration shown above.

Look under the heading "Deceleration." There is a minor typographical mistake. The final velocity of the car after applying the brakes is 20m/s rather than 200m/s.

ReplyDeleteHi Hamza,

DeleteThanks for pointing that out. It has been corrected now.

thanks for it :)

ReplyDeleteI still not understand uniform acceleration .can someone help me!!!

ReplyDeleteUniform acceleration is very simple. If an objects velocity is increasing at constant rate then it has uniform acceleration. eg. In 2sec a car has a velocity of 5m/s, in 4sec 10m/s, in 6sec 15m/s.....and so on. The velocity is increasing at a constant rate of 5m/s.

ReplyDeleteHow to calculate non-uniform velocity ?...there is'nt explanation about it

ReplyDeleteThank You for this precious explanation. Love it and it was really helpfuL.

ReplyDeletewhats the difference between a constant velocity and a uniform acceleration?

ReplyDeleteWhats the difference between constant velocity and uniform velocity?

ReplyDeleteIt's a nice approach to uniform acceleration and non uniform acceleration. I really like it. Thanks for sharing it.

ReplyDelete