Question

A bus decreases its speed from 80 km per hour from 60 km per hour in 5 seconds calculate the acceleration of the bus

Answer 1

u= initial velocity= 80 km/h = 22.2 m/s
v= final velocity = 60 km/h = 16.7 m/s
t= time = 5 s
a= acceleration = ?

a=v-u/t
a= 16.7-22.2/5
a= -5.5/5
Therefore, a=-1.1 m/s^2

Answer 2

Given: The initial speed of the bus, u = 80km

           The final speed of the bus, v = 60 km

           Time taken, t = 5s

To Find: acceleration of the bus, a.

Solution:

To calculate a, the formula used:

• v = u + a x t ⇒ First Law of Motion

or, it can be written as-

• a = v- u / t

Here, v-u = 60-80

               = -20km/hr

Now covert, km/hr into m/s

1 km = 1000m

1 hr = 3600s

1 km/hr = 1000/3600

            = 5/18 m/s

So, -20km/hr = -20x 5 / 18

                      = - 5.55 m/s

v- u = -5.55 m/s

Applying the formula for a :

a = -5.55 / 5

  = -1.11m/s²

a = -1.11 m/s²

Negative sign shows that velocity of the bus is decreasing.

Hence, the acceleration of the bus is -1.11 m/s².