Question

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

I hope you like my answer............

Answer 2

Answer:

In this problem, we will have to change the speeds of bus from km h–1 (kilometres per hour) to m s–1  (metres per second) because the time is given in seconds.

Now, Initial speed of bus, u = 80 km h–1

80 1000 m

60 60 s

× = ×

= 22.22 m s–1 ... (1)

Final speed of bus, v = 60 km h–1

60 1000 m

60 60 s

× = ×

= 16.66 m s–1 ... (2)

And, Time taken, t = 5 s ...(3)

Now, Acceleration, u

a

t

− = v

16.66 22.22

5

a − =

5.56

5

a − =

a = – 1.11 m s–2

Thus, the acceleration of the bus is, –1.11 m s–2. The minus sign for acceleration shows that it is actually  negative acceleration or retardation.