Sol:

The initial speed of the var is 54 km/hr or 15 m/s.

In reaction time the body moves with the speed 54 km/hr = 15 m/sec

Distance travelled in this time is

S_{1} = u * t

S_{1} = 15 * 0.2 = 3m

When brakes are applied.

u = 15 m/s

v = 0

a = – 6 $$m/s^{2}$$ $$v^{2} = u^{2} + 2as$$ $$S_{2} = \frac{v^{2} – u^{2}}{2a}$$ $$\Rightarrow \frac{0 – 15^{2}}{2 (-6)}$$ $$\Rightarrow 18.75 m$$

Total distance$$S = S_{1} + S_{2}$$ $$\Rightarrow 3 + 18.75$$ $$\Rightarrow 21.75 = 22 m$$

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