Acceleration is defined as the change in velocity with respect to time. Acceleration is vector quantity. The SI unit of acceleration is m/s2.
Acceleration = Change in velocity/time
If the initial velocity is ‘u’, and after time ‘t’ the velocity is final velocity. So change in velocity is, final velocity – Initial velocity.
Acceleration (a) = Final velocity – Initial velocity/time
∴ a = v-u/t
E.g:
(1) Slide in the park. While sliding down velocity is less at top increases at top increases of middle and zero at end.
(2) The fruits is falling down.
Numericals on Acceleration Formula
A bus slows down from a speed of 68 km/h to reset in 20 seconds. What is acceleration of bus in m/s2.
Ans: Initial velocity ‘u’ 68 km/h
final velocity ‘v’ = 0 km/h
convert 68 km/h into m/s
1 km = 1000 m
So, 1000/20 = 50 m/s
Initial velocity ‘u’ = 68 km/h
= 68 × 50 m/s
= 3400 m/s
Final velocity ‘v’ = 0 km/h
= 0 × 50 = 0 m/s
Now acceleration,
Acceleration = Final velocity – initial velocity /time
= v – u/t
= 0 – 3400/20
= – 3400/20 = -170 m/s2
Acceleration = -170 m/s2
Here velocity is decreases with time and direction is opposite to direction of velocity.
