Question

A bus is moving with 60 Km/h and driver applied the brake the brake then speed is decreased by 20 km/h in 6 sec. Calculate the acceleration.​

Answer 1

Answer :-

Acceleration of the bus is -1.85 m/s² .

Explanation :-

We have :-

→ Initial speed (u) = 60 km/h

→ Final speed (v) = 20 km/h

→ Time (t) = 6 seconds

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Firstly, let's convert the unit of initial and final speeds of the bus from km/h to m/s.

Initial speed :-

⇒ 1 km/h = 5/18 m/s

⇒ 60 km/h = 60 × 5/18

⇒ 300/18 m/s

⇒ 16.67 m/s

Final speed :-

⇒ 20 km/h = 20 × 5/18

⇒ 100/18

⇒ 5.56 m/s

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Now, let's calculate acceleration of the bus by using the 1st equation of motion .

v = u + at

⇒ 5.56 = 16.67 + a(6)

⇒ 5.56 - 16.67 = 6a

⇒ 6a = -11.11

⇒ a = -11.11/6

⇒ a = -1.85 m/s²

Answer 2

Answer:

Given :-

• A bus is moving with 60 km/h and driver applied the brake then the speed is decreased by 20 km/h in 6 seconds.

To Find :-

• What is the acceleration.

Formula Used :-

$\clubsuit$ Acceleration Formula :

$\mapsto \sf\boxed{\bold{\pink{a =\: \dfrac{v - u}{t}}}}$

where,

• a = Acceleration
• v = Final Velocity
• u = Initial Velocity
• t = Time

Solution :-

First, we have to convert km/h into m/s :

${\normalsize{\bold{\purple{\underline{\bigstar\: In\: case\: of\: Initial\: velocity\: :-}}}}}$

$\implies \sf Initial\: Velocity =\: 60\: km/h$

$\implies \sf Initial\: Velocity =\: 60 \times \dfrac{5}{18}\: m/s\: \: \bigg\lgroup \sf\bold{1\: km/h =\: \dfrac{5}{18}\: m/s}\bigg\rgroup$

$\implies \sf Initial\: Velocity =\: \dfrac{60 \times 5}{18}\: m/s$

$\implies \sf Initial\: Velocity =\: \dfrac{300}{18}\: m/s$

$\implies \sf\bold{\green{Initial\: Velocity =\: 16.67\: m/s}}$

${\normalsize{\bold{\purple{\underline{\bigstar\: In\: case\: of\: final\: velocity\: :-}}}}}$

$\implies \sf Final\: Velocity =\: 20\: km/h$

$\implies \sf Final\: Velocity =\: 20 \times \dfrac{5}{18}\: m/s\: \: \bigg\lgroup \sf\bold{1\: km/h =\: \dfrac{5}{18}\: m/s}\bigg\rgroup$

$\implies \sf Final\: Velocity =\: \dfrac{20 \times 5}{18}\: m/s$

$\implies \sf Final\: Velocity =\: \dfrac{100}{18}\: m/s$

$\implies \sf\bold{\green{Final\: Velocity =\: 5.56\: m/s}}$

Now, we have to find the value of acceleration :

Given :

• Initial Velocity (u) = 16.67 m/s
• Final Velocity (v) = 5.56 m/s
• Time (t) = 6 seconds

According to the question by using the formula we get,

$\longrightarrow \sf a =\: \dfrac{5.56 - 16.67}{6}$

$\longrightarrow \sf a =\: \dfrac{\bigg(\dfrac{556}{100}\bigg) - \bigg(\dfrac{1667}{100}\bigg)}{6}$

$\longrightarrow \sf a =\: \dfrac{\bigg(\dfrac{556 - 1667}{100}\bigg)}{6}$

$\longrightarrow \sf a =\: \dfrac{\bigg(\dfrac{- 1111}{100}\bigg)}{6}$

$\longrightarrow \sf a =\: \dfrac{- 11.11}{6}$

$\longrightarrow \sf\bold{\red{a =\: - 1.85\: m/s^2}}$

$\therefore$ The acceleration is - 1.85 m/s².