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

Answer 1

Answer:

Given, u =80km/h = 80 × 5/18 = 200/9 m/s

v = 60 km/h = 60 × 5/18 = 150/9 m/s

t = 5s

.°. Acceleration,

$a = \frac{v - u}{t} \\ \: \: \: \: = \frac{ \frac{150}{8} - \frac{200}{8} }{5} \\ \: \: \: \: = \frac{ - 50}{40} \\ \: \: \: \: = - 1.25m {s}^{ - 1}$

Answer 2

Given:-

Initial velocity ,u = 80km/h

Final velocity ,v = 60km/h

Time taken ,t = 5 s

To Find:-

Acceleration ,a

Solution:-

⠀⠀⠀⠀⠀⠀⠀⠀⠀According to the Question

Firstly we change the unit of velocity .

Initial velocity ,u = 80 × 5/18 = 400/18 = 22.22 m/s

Final velocity ,v = 60 × 5/18 = 300/18 = 16.66

As we know that acceleration is defined as the rate of change in velocity

a = v-u/t

where,

v denote final velocity

u denote initial velocity

t denote time taken

a denote acceleration

Substitute the value we get

a = 16.66-22.22/5

a = -5.56/5

a = -1.12 m/s²

here, negative sign show retardation

Hence, the acceleration of the bus is approximately 1.12 m/s²