Question

a scooter with speed of 36km/hr come to the rest in 5sec. what is the deacceleration

Answer 1

Answer:

initial velocity (u)=36÷5/8

=22.5m/s

time= 5sec

final velocity (v)= 0

deceleration = v-u/t

= 0-22.5/5

=-4.5m/s^2

Explanation:

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Answer 2

Answer:

+ 2 m/s²

Explanation:

As per the provided information in the given question, we have :

• Initial velocity (u) = 36 km/h
• Final velocity (v) = 0 m/s [As it comes to rest.]
• Time taken (t) = 5 seconds

We've been asked to calculate the deceleration.

In order to calculate the deceleration of the scooter, firstly we need to calculate the acceleration of the scooter. We'll find the acceleration of the scooter of the car by using the first equation of motion.

By using the first equation of motion,

$\bigstar \quad \underline{\boxed{\pmb{\frak{v = u + at}} }}$

• v denotes final velocity
• u denotes initial velocity
• a denotes acceleration
• t denotes time

Before substituting the values in the formula, firstly we need to convert the velocity into m/s.

$\longrightarrow \sf{\quad { u = 36 \; km \: h^{-1}}}$

• 1 km/h = 5/18 m/s

$\longrightarrow \sf{\quad { u = \Bigg \{ 36 \times \dfrac{5}{18} \Bigg \} \; m \: s^{-1}}}$

$\longrightarrow \sf{\quad { u = \Bigg \{ 2 \times 5 \Bigg \} m \: s^{-1}}}$

$\longrightarrow \quad\underline{\boxed { \sf u = 10 \; m \: s^{-1}}}$

$\rule{200}2$

Now, substitute the values in the formula.

$\longrightarrow \sf{\quad { 0 = 10 + 5a}}$

$\longrightarrow \sf{\quad { 0 - 10 = 5a}}$

$\longrightarrow \sf{\quad { - 10 = 5a}}$

$\longrightarrow \sf{\quad { \cancel{\dfrac{- 10}{5}}= a}}$

$\longrightarrow \sf{\quad { - 2 \; m \: s^{-2} = a}}$

As we know that retardation is the acceleration with negative sign, so :

$\longrightarrow \sf{\quad { -(- 2) \; m \: s^{-2} = Retardation}}$

$\longrightarrow \quad \underline{\boxed{ \textbf{\textsf{ + 2\;m }}\: \textbf{\textsf{s}}^{\textbf{\textsf{-2}}} = \textbf{\textsf{Retardation}}}}$

Therefore, deceleration is + 2 m/s².

$\rule{200}2$

Learn More:

Equations of motion :

$\boxed{ \begin{array}{cc} \pmb{\sf{ \quad \: v = u + at \quad}} \\ \\ \pmb{\sf{ \quad \: s= ut + \cfrac{1}{2}a{t}^{2} \quad \: } } \\ \\ \pmb{\sf{ \quad \: {v}^{2} - {u}^{2} = 2as \quad \:}}\end{array}}$

• v denotes final velocity
• u denotes initial velocity
• a denotes acceleration
• t denotes time
• s denotes distance