Question

a toy car initially moving with a uniform velocity of 18 kilometre per hour comes to stop in 2 seconds... find the retardation of the car in SI units

Answer 1

Intial velocity = 18kmph = 5mps
final velocity = 0 ( as body stops)
time taken = 2 sec

acceleration = change in velocitiy/time

acceleration
= (final velocity- intial velocity)/time

a. = 0-5/2 = -2.5 mpss

negative acceleration is also called retardation

so retardation = 2.5mpss

where mpss is meter per second square

Answer 2

$\huge \underline \mathfrak \purple{hello \: mate}$

given,

initial velocity (u) = 18km/h

final velocity (v) = 0km/h

time (t) = 2 s

acceleration/retardation (a) =?

according to the question,

initial velocity = 18km/h to m/s

= 18 × 5/18 m/s

= 5 m/s.

we know that,

a = (v-u)/t

a = (0 - 5) / 2

a = -5/2

a = -2.5m/s².

The acceleration is also called retardation so,

$\tt \red{retardation \: = 2.5m{s}^{ - 2}}$