Question

A bus starts from rest and attains 40 km/hr velocity after 10 second s. Calculate the accelaaccele in km/hr and ms^{​​​​​-2}

Answer 1

Bus starts from rest , it means initial velocity of bus , u = 0
Bus attains 40 km/h velocity after 10sec
final velocity of bus , v = 40 km/h = 40 × 5/18 m/s [ we know, 1 km/h = 5/18 m/s ]
v = 100/9 m/s
Time taken by bus , t = 10sec

we should use formula,
v = u + at
from above , v = 100/9 m/s , u = 0 and t = 10sec
Now, 100/9 = 0 + a × 10
⇒ 100/9 = 10a
⇒ a = 10/9 m/s²
Hence, acceleration of bus in m/s² = 10/9 m/s²

Now, acceleration of bus in Km/h²
v = 40 km/h , u = 0 and t = 10sec = 10/3600 hr = 1/360 hr
Now, from formula ,
V = u + at
40 = 0 + a × 1/360
40 = a/360
a = 40 × 360 = 14400 km/h²

Hence, (a) 14400 km/h²
(b) 10/9 m/s²