Question

4. A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.​

Answer 1

A bus decreases its speed from 80 km/h to 60 km/h in 5 s.

Given that, starting speed means the initial velocity (u) of the bus is 80 km/hr.

And ending or final velocity (v) of the bus is 60 km/hr.

Also given that, time (t) is 5 seconds.

We have to find the acceleration of the bus.

Using First Equation of Motion i.e.

v = u + at

Given time is in seconds and speed is in km/hr. So, convert the speed in m/s.

Initially velocity (u) = 80 × 5/18 = 22.22 m/s

Final velocity (v) = 60 × 5/18 = 16.67 m/s

Substitute them in the above formula

→ 16.67 = 22.22 + a(5)

→ 16.67 - 22.22 = 5a

→ -5.55 = 5a

→ -1.11 = a

(Negative sign shows the deceleration or retardation)

Therefore, the deceleration of the bus is -1.11 m/s².

Answer 2

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QUESTION :

4. A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.

SOLUTION :

From the above Question, we can get the following information...

U = 80 kmph = 80 × { 5 / 18 } m / s = 22.22 m / s

V = 60 kmph = 60 × { 5 / 18 } m / s = 16.67 m / s

Time, T = 5 s

According to Newton's First Equation Of Motion,

a = { V - U } / t

=> a = { 22.22 - 16.67 } / 5 m / s ^ 2

=> a = -1.11 m / s ^ 2

So, the deceleration of the bus is 1.11 m / s ^ 2.

ANSWER :

The deceleration of the bus is 1.11 m / s ^ 2.