Question

If bus travelling at 20m/s is subjected to a deceleration of 5m/s2 how long will it take to come to rest

Answer 1

Given ,

Initial velocity (u) = 20 m/s

Deceleration (a) = -5 m/s²

Final velocity (v) = 0 m/s

We know that , the first equation of motion is given by

$\star \: \: \sf v = u + at$

Thus ,

$\Rightarrow \sf 0 = 20 + (-5)t \\ \\ \Rightarrow \sf</p><p>-20 = -5t \\ \\ \Rightarrow \sf</p><p>s = 4 \: \: s</p><p>$

$\therefore \sf \underline{ \bold{The \: required \: \: time \: is \: 4 \: sec}}$

Answer 2

$\rule{200}2$

$\large\bold{\mathtt{QUESTION}}$

➡ If bus travelling at 20m/s is subjected to a deceleration of $\sf 5m/{s}^{2}$ how long will it take to come to rest ?

$\rule{200}2$

$\large\bold{\mathtt{SOLUTION}}$

⚡GIVEN -

↪Initial Velocity → 20 m/s

↪Final Velocity → 0 m/s ( as it comes to rest )

↪Deceleration → - 5 m/s ( -ve sign shows negative acceleration )

⚡TO FIND -

↪Time taken

☯ From first equation of motion -

✳ $\sf v\:=u\:+\:at$

↪$\sf0 \:= \:20\: +\: ( \:-\:5)\:t$

↪$\sf \:-\:20 \:= \:-\:5t$

↪$\sf t \:= \dfrac{-20}{-5}$

$\sf \:\:\:\:\:\:\:\:\:\:\:{\underline{\red{TIME\:=\: 4\:seconds}}}$

$\sf Therefore, time\:taken\:is\:4\:seconds$

$\rule{200}2$