Acceleration

Acceleration is the change in velocity with time.

Vector quantity

Formula: a = ^{(v - u)}⁄_t

where v = final velocity,
            u = initital velocity,
             t = time taken.

Unit: m/s²

Two types:
1. Positive acceleration: change in velocity is in the same direction as the velocity.   
   => Speed is increasing. 
2. Negative acceleration: change in velocity is in the opposite direction to the velocity
   => Speed is decreasing. 
   => Also known as deceleration or retardation

For example:

Positive acceleration => Car speeding up Velocity increases from 0. At t = 0s, v = 0ms-1, At t = 1s, v = 5ms-1, a = (5-0)⁄(1-0) = 5.0 ms-2	Negative acceleration => Car slowing down Velocity decreases to 0. At t = 0s, v = 5ms-1, At t = 1s, v = 0ms-1, a =(0-5)⁄(1-0)= -5.0 ms-2

Note:
(1) If the direction of the object changes, it is undergoing acceleration as change in direction = change in velocity = acceleration.
(2) Decreasing acceleration ≠ deceleration. It means increasing speed at decreasing rate.

Previous: Speed v.s Velocity

Next: Kinematics Graph