Question

I GIVE MEDALS.
You drop a rock down a well that is 11.5 m deep. How long does it take the rock to hit the bottom of the well?

A. 3.1 s
B. 2.8 s
C. 1.5 s
D. 2.3 s

Answer 1

second equation of kinematics is \[s=ut+(\frac{ 1 }{ 2 } at ^{2})\]

since \[u=0\]; \[t=\sqrt{\frac{ 2s }{ g }}\]

put \[s=11.5, g=9.8 \] which gives \[t=1.5;\] so the answer is 'c'.