Question

A bus decreases its speed from 80km/h to 60km/h in 5sec. Find acceleration of bus. (Convert km/h to m/s by using 1km/h =5/18 m/s).

Answer 1

Given :

• Initially speed of bus (u) = 80km/h
• Final speed of bus (v) = 60km/h
• In time (t) = 5s

To Find :

• Acceleration (a)

Formula Used :

$\bullet\underline{\boxed{\sf v = u+at}}$

Solution :

➞ Convert km/h to m/s

$\implies{\sf u = 80\: km/h }$

$\implies{\sf 80 \times \dfrac{5}{18}}$

$\implies{\bf u = 22.2\: m/s }$

$\implies{\sf v = 60 \times \dfrac{5}{18}}$

$\implies{\bf v = 16.5 \: m/s }$

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$\implies{\sf v = u + at }$

$\implies{\sf 16.4 = 22.2 + a\times 5}$

$\implies{\sf a =\dfrac{16.4-22.2}{5} }$

$\implies{\sf a =\dfrac{-5.8}{5} }$

$\implies{\bf a = -1.16\: m/s^2 }$

Negative sign indicates deceleration

Answer :

Deceleration of bus is -1.16 m/s²

➞ Some related formula

• v = u + at
• s = ut + ½at²
• v² = u² +2as

Answer 2

Hello freindwa!

intial speed (u) = 80km/h → 80× 5/18 = 200/9 m/s

final speed (v) = 60km/h = 60× 5/18 = 150/9 m/s

t = 5 sec

avg acceleration = v- u /t

= ( 150/9-200/9 )÷5 = 50/45 = - 1.12 m/s²