Question

please help me guys
it's urgent​

Answer 1

$\huge\mathcal{\fcolorbox{cyan}{black}{\pink{ANSWER}}}$

Given,

initial velocity u = 18 km/h

= (18 x 1000) ÷ 3600 m/s

= 5 m/s

final velocity v = 0 m/s

time to stop t = 2.5 sec

retardation a = to find

we know that,

$v = u + at \\ \implies \: a \: = \frac{v - u}{t} \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = \frac{0 - 5}{2.5} \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: \: = - 2 \: \: m {s}^{ - 2}$

Answer 2

Answer:

Question :-

• A bus running at a speed of 18 km/h is stopped in 2.5 seconds by applying brakes. Calculate the retardation produced.

Given :-

• A bus running at a speed of 18 km/h is stopped in 2.5 seconds by applying brakes.

To Find :-

• What is the retardation produced.

Formula Used :-

$\clubsuit$ First Equation Of Motion Formula :

$\mapsto \sf \boxed{\bold{\pink{v =\: u + at}}}$

where,

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

Solution :-

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

$\implies \sf Initial\: Velocity =\: 18\: km/h$

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

$\implies \sf \bold{\purple{Initial\: Velocity =\: 5\: m/s}}$

Given :

• Initial Velocity (u) = 5 m/s
• Final Velocity (v) = 0 m/s
• Time (t) = 2.5 seconds

According to the question by using the formula we get,

$\longrightarrow \sf 0 =\: 5 + a(2.5)$

$\longrightarrow \sf 0 - 5 =\: a(2.5)$

$\longrightarrow \sf - 5 =\: a(2.5)$

$\longrightarrow \sf \dfrac{- 5}{2.5} =\: a$

$\longrightarrow \sf \dfrac{- 5}{\dfrac{25}{10}} =\: a$

$\longrightarrow \sf \dfrac{- 5}{1} \times \dfrac{10}{25} =\: a$

$\longrightarrow \sf \dfrac{- \cancel{50}}{\cancel{25}} =\: a$

$\longrightarrow \sf - 2 =\: a$

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

Hence, the retardation produced is :

$\mapsto \sf\bold{\pink{Retardation :-}}$

• Retardation means negetive acceleration.

$\longrightarrow \sf Retardation =\: -(- 2\: m/s^2)$

$\longrightarrow\sf\bold{\red{Retardation =\: 2\: m/s^2}}$

$\therefore$ The retardation produced in a bus is 2 m/s².