A bus decreases its speed from 80km/h to 60 km/h in 5 seconds. Find the acceleration of the bus.

-Shresthi Goyal, Subject Matter Expert at Edumarz

Answer:  Converting units of km/h into m/s

80 km/h = ( 80 ×1000)/ (60×60)

= 800/36 m/s= 200/9 m/s 

60 km/h = (60 ×1000)/(60×60) = (50/3)m/s

Acceleration= Change in velocity/ Time

( 50/3-200/9 ) / 5 = (150-200/9 ) / 5

Acceleration= -50/45 = -10/9 = -1.11

 (minus sign indicates, that bus is retarding)