Question

You drop a 30 g pebble down a well. You hear a splash 2.7 s later. Ignoring air resistance, how deep is the well? Assume g = 9.8 m/s2.

a)0.79 m
b)36 m
c)71 m
d)790 m

Answer 1

Here, you need to apply second equation of Kinematics
S = ut + 1/2 at²
s = at²/2  [ As initial velocity (u) = 0 ]

Now, a = 9.8 m/s²
t = 2.7 s

Substitute their values in the formula:
s = 9.8 × (2.7)² / 2
s = 35.721 m

After rounding-off to the nearest hundredth value, it would be 36 m

Finally, your answer would be option B.

Hope this helps!