Question

The equation of motion of a stone, thrown vertically upwards is $s=ut-6.3t^2$,where the units of s and t are cm and sec. If the stone reaches at maximum height in 3 sec, then u =

• A. 18.9 cm/sec
• B. 12.6 cm/sec
• C. 37.8 cm/sec
• D. None of these

Answer 1

The correct option is C 37.8 cm/sec

Velocity of particle at the maximum height $\frac{ds}{dt}=0\Rightarrow u-12.6t=0\Rightarrow u=12.6t=37.8cm/s$.