Question

bus is moving with a speed of 20m/s brakes are applied and accerlation of minus 5 metre per second square is produced.calculate the time taken for the bus to stop​

Answer 1

Given :

Initial velocity = 20m/s

Acceleration = 5m/s²

Final velocity = zero

To Find :

Time taken by bus to stop.

Solution :

⧪ Acceleration is defined as the rate of change of velocity.

• It us a vector quantity having both magnitude as well as direction.
• It can be positive, negative or zero.
• SI unit : m/s²
• CGS unit : cm/s²

Formula : $\underline{\boxed{\bf{\purple{a=\dfrac{v-u}{t}}}}}$

★ Time taken by body to stop is called stopping time. In this case, velocity of bus is decreasing with time hence acceleration will be negative.

➝ a = (v - u) / t

➝ -5 = (0 - 20) / t

➝ -5 = -20/t

➝ t = 20/5

➝ t = 4 s

Answer 2

Answer:

$\large\bf\underline\color{lime} {\underline{concept - }}$

ᴛʜᴇʀᴇ ɪs ᴀ ʙᴜs ᴡʜɪᴄʜ ɪs ᴍᴏᴠɪɴɢ ᴡɪᴛʜ ᴛʜᴇ sᴘᴇᴇᴅ ᴏғ 20 ᴍ/s ᴀɴᴅ ᴛʜᴇɴ ᴛʜᴇ ʙᴜs ᴀᴘᴘʟʏ ʙʀᴀᴋᴇs. ᴛʜᴇ ᴀᴄᴄᴇʟᴇʀᴀᴛɪᴏɴ ɪs -5 ᴍ/s².

$\large\bf\underline\color{purple} {\underline{To find - }}$

• ᴛʜᴇ ᴛɪᴍᴇ ᴛᴀᴋᴇɴ ғᴏʀ ᴛʜᴇ ʙᴜs ᴛᴏ sᴛᴏᴘ

$\large\sf \underbrace \red{important \: to \: note - }$

• ᴡʜᴇɴᴇᴠᴇʀ ᴛʜᴇ ǫᴜᴇsᴛɪᴏɴ ᴡɪʟʟ ᴍᴇɴᴛɪᴏɴ ᴀʙᴏᴜᴛ ʙʀᴀᴋᴇs ᴛʜᴇ ᴀᴄᴄᴇʟᴇʀᴀᴛɪᴏɴ ᴡɪʟʟ ʙᴇ ᴍɪɴᴜs(- ).
• ғᴏʀ ᴇxᴀᴍᴘʟᴇ 5 ᴍ/s²ᴀᴄᴄᴇʟᴇʀᴀᴛɪᴏɴ ɪs ᴍᴇɴᴛɪᴏɴᴇᴅ, ᴡʜᴇɴ ᴡᴇ ᴡɪʟʟ ᴅᴏ ᴛʜᴇ sᴏʟᴜᴛɪᴏɴ ᴡᴇ ʜᴀᴠᴇ ᴛᴏ ᴡʀɪᴛᴇ -5 ᴍ/s²,
• ɪғ ɪᴛ ʜᴀs ᴀʟʀᴇᴀᴅʏ ᴡʀɪᴛᴛᴇɴ -5 ᴍ/s² ɪɴ ᴛʜᴇ ǫᴜᴇsᴛɪᴏɴ, ᴡᴇ ɴᴏ ɴᴇᴇᴅ ᴛᴏ ᴄʜᴀɴɢᴇ ɪᴛ

$\large\bf\underline\color{lime} {\underline{Solution - }}$

$\\ \bf \blue {it \: is \: in \: the \: attachment}$

$\large\bf\underline\color{lime} {\underline{About formula - }}$

$\\ \bf \bigstar\green{s = vt}\bigstar \\ \\ \bigstar \bf\green{v = u \: + \: at}\bigstar \\ \\ \bf \bigstar \green{s = ut + \frac{1}{2} at {}^{2} }\bigstar \\ \\ \bigstar\bf\green{2as = {v}^{2} - {u}^{2} }\bigstar \\ \\ \bigstar \bf\green{ a = \frac{v - t}{t} }\bigstar$

$\large\dagger \mathtt\red {formula \: will \: be \: used - }\dagger$

$\large\bigstar \bf \pink{a = \frac{v - u}{t} }$

$\bf \color{yellow}{where \: }$

• $\bf \red{a = acceleration }\\ \bf \color{orange}{v = final \: velocity }\\ \bf \color{grey}{ u = initial \: velocity}$