Question

A truck running at 90 km/h is brought to rest over a distance of 25 m. Calculate the retardation
and time for which brakes are applied​

Answer 1

Given :-

A truck running at 90 km/h is brought to rest over a distance of 25 m

To Find :-

Retardation

Time

Solution :-

We know that

1 km/h = 5/18 m/s

90 km/h = 90 × 5/18 = 5 × 5 = 25 m/s

v² - u² = 2as

(0)² - (25)² = 2(a)(25)

0 - 625 = 50a

-625 = 50a

-625/50 = a

-12.5 = a

Now

v = u + at

0 = 25 + (-12.5)t

0 - 25 = -12.5t

-25 = -12.5t

25 = 12.5t

25/12.5 = t

2 = s

Time is 2 second

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Answer 2

Answer:

Retardation = -1620 km/h

Time= 3.6 seconds