Question

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

Answer 1

$acceleration =$

$change \: in \: velocity \: \div time \: taken$

$v - u \div t$

$(80 - 60) \div 5$

$20 \div 5$

$4ms { - }^{2}$

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Answer 2

Given :

• Initial Velocity (u) = 80 km/h
• Final Velocity (v) = 60 km/h
• Time Taken (t) = 5 sec .

To Find :

• Acceleration of the bus .

Solution :

$\longmapsto\tt{Initial\:Velocity(u)=80\times\dfrac{5}{18}=22.22\:m/s}$

$\longmapsto\tt{Final\:Velocity(v)=60\times\dfrac{5}{18}=16.67\:m/s}$

Using 1st Equation :

$\longmapsto\tt\boxed{v=u+at}$

Putting Values :

$\longmapsto\tt{16.67=22.22+a(5)}$

$\longmapsto\tt{16.67-22.22=5a}$

$\longmapsto\tt{-5.55=5a}$

$\longmapsto\tt{a=\cancel\dfrac{-5.55}{5}}$

$\longmapsto\tt\bf{a=-1.11\:{m/s}^{2}}$

So , The Acceleration of the bus is -1.11 m/s² ....

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Three Equations Of Motion :

• v = u + at
• s = ut + 1/2 at²
• v² - u² = 2as

Here :

• v = Final Velocity
• u = Initial Velocity
• t = Time Taken
• a = Acceleration
• s = Distance Travelled

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