Question

a car travelling with a speed of 20 km per hour comes into rest in 0.5 hours .what will be the value of retardation.

Answer 1

Information provided to us:

Initial velocity, u = 20 km/h
Final velocity, v = 0 km/h
Time, t = 0.5 hours

Hence,

Acceleration, a = ( v - u ) / t
a = ( 0 - 20 ) / 0.5
a = - 20 / 0.5
a = - 200 / 5
a = - 40 km/h^2

We know that negative acceleration is retardation so,

Retardation, r = - a
r = - ( - 40 )
Retardation = 40 km / h ^ 2

Answer 2

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Initial velocity = 20 km/h

Final velocity = 0 km/h

Time = 0.5 hours

Therefore,

Acceleration = $\bf\huge\frac{V - U}{t}$

Acceleration = $\bf\huge\frac{0 - 20}{0.5}$

Acceleration = $\bf\huge\frac{-20}{0.5}$

Acceleration = $\bf\huge\frac{- 200}{5}$

Acceleration = - 40 km/h

Negative acceleration is retardation :-

Retardation = - ( - 40 )

Retardation = 40 km / h

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