16. A car moving with a speed of 40 km/h can be stopped by applying brakes at least after 2 m. If the same car is moving with a speed of 80 km/h, what is the minimum stopping distance?
(a) 8 m
(b) 6 m
(c) 4 m
(d) 2 m
Answer : (a) 8 m
\( v^2 = u^2 + 2as \)
\( \rightarrow 0 = u^2 - 2a d_{Braking} \)
\( \rightarrow d_{Braking} = \)\( \frac{u^2}{2a} \)
\( d_1 = 2 \)
\( u_1 = 40\ \text{km/h} \)
\( u_2 = 80\ \text{km/h} \)
\( \frac{d_1}{d_2}\) \( = \) \( \frac{ \frac{40^2}{2a} }{ \frac{80^2}{2a} } \)
\( \rightarrow \) \( \frac{2}{d_2} \) \( = \) \( \frac{40^2}{80^2} \)
\( d_2 = 2 \times \) \( \frac{80^2}{40^2} \)
\( d_2 = 2 \times 4 \)
\( d_2 = 8\ \text{m} \)
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