Question

A bus decreases its speed from 80km/h to 60 km/h is 5s. Find the acceleration of a bus

Answer 1

Initial velocity of the bus(u) = 80 km/hr
Final velocity of the bus (v) = 60 km/hr
Time taken (t) = 5 sec.

According to the formula ,
v = u + at
There fore,

$a = \frac{v - u}{t} \\ = \frac{60 - 80}{5} km {hr}^{ - 2} \\ = \frac{ - 20}{5} km {hr}^{ - 2} \\ = - 4 \: km {hr}^{ - 2}$
Here you can convert the acceleration from km/hr sq. to m/s sq. by dividing -4 km/hr sq. by 5/18.
Here the'-' sign denotes deceleration or retardation.