If a ball is thrown vertically upwards with speed $u$, the velocity of the ball $t$ seconds before r

Question

If a ball is thrown vertically upwards with speed $u$, the velocity of the ball $t$ seconds before reaching its highest point is

Professor PC Thomas Classes · Answer

(b) : Let total time of ascent be $T = \frac{u}{g}$. \ The time instant $t$ seconds before reaching the highest point is $t' = T - t$. \ Velocity at this instant is $v = u - g t' = u - g(T - t) = u - g\left(\frac{u}{g} - tight) = u - u + gt = gt$.