Question

a motor car moving with a velocity of 54km/hr is brought to rest in 5sec and 30 meter find the retardation in each case​

Answer 1

Given:

A motor car moving with a velocity of 54km/hr is brought to rest in 5sec and 30 meter.

To find:

Retardation of car in each case ?

Calculation:

First , let's convert unit of velocity from km/hr to m/s : simply multiply km/hr value with 5/18.

• 54 km/hr = 54 × 5/18 = 15 m/s.

1st case:

$v = u + at$

$\implies \: 0 = 15 + a(5)$

$\implies \: 5a= - 15$

$\implies \:a= - 3 \: m/ {s}^{2}$

So, acceleration is -3 m/s².

2nd case:

${v}^{2} = {u}^{2} + 2as$

$\implies \: {0}^{2} = {(15)}^{2} + 2a(30)$

$\implies \: 60a = - 225$

$\implies \: a = - 3.75 \: m/ {s}^{2}$

So, acceleration is 3.75 m/s².