Question.
A bus decreases its speed from 80 km h–1 to 60 km h–1 in 5 s. Find the acceleration of the bus.
A bus decreases its speed from 80 km h–1 to 60 km h–1 in 5 s. Find the acceleration of the bus.
Solution:
Given $t=5 \mathrm{~s}$
Initial speed of bus
$\mathrm{u}=80 \mathrm{~km} \mathrm{~h}^{-1}=80 \times \frac{5}{18}=22.2 \mathrm{~ms}^{-1}$
Final speed of the bus
$\mathrm{v}=60 \mathrm{~km} \mathrm{~h}^{-1}=60 \times \frac{5}{18}=16.6 \mathrm{~ms}^{-1}$
Now acceleration is given by the relation
$\mathrm{a}=\frac{\mathrm{v}-\mathrm{u}}{\mathrm{t}}=\frac{16.6-22.2}{5}=-1.1 \mathrm{~ms}^{-2}$
Given $t=5 \mathrm{~s}$
Initial speed of bus
$\mathrm{u}=80 \mathrm{~km} \mathrm{~h}^{-1}=80 \times \frac{5}{18}=22.2 \mathrm{~ms}^{-1}$
Final speed of the bus
$\mathrm{v}=60 \mathrm{~km} \mathrm{~h}^{-1}=60 \times \frac{5}{18}=16.6 \mathrm{~ms}^{-1}$
Now acceleration is given by the relation
$\mathrm{a}=\frac{\mathrm{v}-\mathrm{u}}{\mathrm{t}}=\frac{16.6-22.2}{5}=-1.1 \mathrm{~ms}^{-2}$
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