Explanation: \(\text{Hints: } v^2 = u^2 - 2as, \, \text{পরে } u = at \, \text{এবং } F = ma\)
\(\text{Solve: এখানে, আদিবেগ } u = 72 \, \text{km/hr} = \frac{72 \times 1000}{3600} \, \text{m/s} = 20 \, \text{ms}^{-1}\)
\(\text{সরণ, } s = (40.5 - 0.5) \, \text{m} = 40 \, \text{m}; \, \text{শেষবেগ, } v = 0\)
\(\text{আমরা জানি, } v^2 = u^2 - 2as \implies 0 = u^2 - 2as \implies a = \frac{u^2}{2s} \implies a = \frac{(20)^2}{2 \times 40} \implies a = 5 \, \text{ms}^{-2}\)
\(\text{গাড়ি থামাতে সময়, } v = u - at \implies 0 = 20 - 5t \implies t = \frac{u}{a} = \frac{20}{5} = 4 \, \text{sec}\)
\(\text{প্রয়োজনীয় বল, } F = ma = 1000 \times 5 = 5000 \, \text{N} = 5 \times 10^3 \, \text{N}\)
\(\text{Ans. (C)}\)
