Question

a bus decrease its speed from 90 km to 60 km in 5 second find the acclaration of the bus​

Answer 1

Given :

➳ Initial velocity = 90km/h

➳ Final velocity = 60km/h

➳ Time interval = 5s

To Find :

⟶ Acceleration of bus.

Concept :

➝ Acceleration is defined as the rate of change in velocity.

➝ It is a vector quantity having both magnitude as well as direction.

➝ It can be positive, negative or zero.

➝ SI unit : m/s²

✴ First equation of kinematics :

$\bigstar\:\underline{\boxed{\bf{v=u+at}}}$

Where,

➠ v denotes final velocity

➠ u denotes initial velocity

➠ a denotes acceleration

➠ t denotes time

Conversion :

➾ 1km/h = 5/18m/s

➾ 90km/h = 90×5/18 = 25m/s

➾ 60km/h = 60×5/18 = 16.67m/s

Calculation :

$\longrightarrow\tt\:v=u+at\\ \\ \longrightarrow\tt\:16.67=25+a(5)\\ \\ \longrightarrow\tt\:5a=16.67-25\\ \\ \longrightarrow\tt\:a=\dfrac{-8.33}{5}\\ \\ \longrightarrow\boxed{\bf{a=-1.67\:ms^{-2}}}$

[Note : -ve sign of a denotes retardation.]

Answer 2

ANSWER :-

We have to find the acclaration of bus whose speed is decreases 90 km/h to 60 km/h in 5 second.

For solving these problems we must know the Newton's equation of motions - -

Here, we use (I) Equation of motion.

(I) Equation of motion i.e

• V = U + A T

Where,

V = Final velocity

U = Inital velocity

A = Accelaration

T= Time

Given,

• Inital velocity = 90km/hour

• Final velocity = 60 km/hour

Using the Newton's first equation of motion - -

V = U + A T

60 km/hour = 90 km/hour + A × 5 second

- A × 5 second = 25 m/s - 16.67 m/s

- A = 8.33 m/s ÷ ( 5 second )

- A = 1.66 m/s^2

A = - 1.66 m/s^2

[ Negative sign shows retardation. ]

Hence, The Accelaration of the bus is

- 1.66 m/s^2