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# A bus decreases its speed from 80 km h–1 to 60 km h–1 in 5 s. Find the acceleration of the bus.

Given, initial speed of bus(u) = 80 km h–1 $$= 80 ×$$ $$5 \over 18$$ $$= 22.22$$ m/s

final speed of bus(v) = 60 km h–1 $$= 60 ×$$ $$5 \over 18$$ $$= 16.66$$ m/s

Time taken = 5 s

We know that,
a = $$v - u \over t$$
= $$16.66 - 22.22 \over 5$$
= $$- 1.112 \ m/s^2$$

$$\therefore a = - 1.112 \ m/s^2$$

The negative sign indicates that the bus is actually not accelerating but retarding.