Question

Find the initial velocity of a car which is stopped in 10 seconds by applying brakes. The retardation due to
brakes is 2.5 m/s2? ​

Answer 1

To FinD :-

• The initial velocity of a car .

$\red{\frak{ Given}}\begin{cases} \textsf{ A car is put to rest .}\\\textsf{ Time taken to stop is 10 s .}\\\textsf{ The retardation of the car is 2.5 m/s ^{\sf 2} .}\end{cases}$

Let us take the initial Velocity of the car be u . Here the car is put to rest in 10s with a retardation of 2.5m/s² . So here we can use the first equation of motion which is ,

$\sf:\implies\pink{ v = u + at }\\\\\sf:\implies 0m/s = u + (-2.5 m/s^2)(10s ) \\\\\sf:\implies 0m/s = u - 25m/s \\\\\sf:\implies u = 0 + 25m/s^2 \\\\\sf:\implies\underset{\blue{\sf Required \ Speed}}{\underbrace{\boxed{\pink{\frak {Initial \ velocity= 25m/s }}}}}$

Answer 2

${Answer}$

Step by step explanation:-

Given :-

• Time taken by body is 10seconds
• Retardation of a body is 2.5m/s²

To find :-

Initial velocity of body

Formula to know:-

From equations of motion ,

v = u + at

Where,

• v is the final velocity
• u is the Initial velocity
• a is the acceleration
• t is the time

Solution :-

Here the body stopped after applied brakes That means the body come into rest So, final velocity of a body is 0

Plugging values :-

Retardation is 2.5m/s² then acceleration will be -2.5m/s²

v = u + at

• v = 0 m/s
• t = 10sec
• u = ?
• a = -2.5m/s²

0 m/s = u + (-2.5)m/s² (10) s

0 = u - 25 m/s

u - 25m/s = 0

u = 25m/s

So, Initial velocity of a body is 25m/s

Know more equations of motion:-

• s = ut+ 1/2at²
• v² - u² = 2as
• s = vt - 1/2 at²
• v²-u² /2s = a
• u = v-at