Question

A bus decrease its speed from 80 kilometre per hour to 60 kilometre per hour in 5 second. Find the acceleration of the bus.

Answer 1

Answer:

Given:

Initial velocity = 80 km/hr

Final velocity = 60 km/hr

Time taken = 5 sec

To find:

Acceleration of the bus

Concept:

Acceleration refers to instantaneous change in velocity with respect to time. Acceleration is a vector quantity , having both direction and magnitude.

Since acceleration os actually decreasing the velocity, it's better to call it as retardation or deceleration.

A negative sign in front of acceleration denotes that , it's direction is opposite to that of velocity.

Conversion:

80 km/hr = 22.22 m/s and

60 km/hr = 16.67 m/s

Calculation:

$v = u + at$

$= > a = \dfrac{v - u}{t}$

$= > a = \dfrac{(16.67 - 22.22)}{5}$

$= > a = \dfrac{( - 5.55)}{5}$

$= > a = - 1.11 \: m {s}^{ - 2}$

So final answer :

$\boxed{ \red{ \huge{a = - 1.11 \: m {s}^{ - 2} }}}$

Answer 2

$\Large{\underline{\underline{\bf{Solution :}}}}$

We know that,

$\Large{\implies{\boxed{\boxed{\sf{a = \frac{v - u}{t}}}}}}$

Where,

• a is acceleration
• v is inital velocity = 80 km/h = 22.22 m/s
• u is final velcoity = 60 km/h = 16.67 m/s
• t is time taken = 5 s

______________[Put Values]

$\sf{→ a = \frac{22.22 - 26.67}{5}} \\ \\ \sf{→a = \frac{-\cancel{5.55}}{\cancel{5}}} \\ \\ \sf{→a = -1.11 \: ms^{-2}} \\ \\ \Large{\implies{\boxed{\boxed{\sf{a = -1.11 \: ms^{-2}}}}}}$

$\rule{200}{2}$

★ Additional information :

★ Uniform Acceleration : When a object is moving with same speed and with same interval of time it is known as uniform Acceleration. For example : A car is moving with 75 km/h. After 1 hour it's speed is same.

★ Non - Uniform Acceleration : When a object is moving with same speed but with different same interval of time it is known as Non - uniform Acceleration. For example : A car is moving with 75 km/h. After 1 hour it's speed is different.