I will assume here that the well is sufficiently short so that the time the sound takes to come from the bottom of the well to our ear is negligible.
Since the pebble moves by uniformly accelerated motion, the distance it covers is given by
where
is the gravitational acceleration
is the time the pebble takes to reach the bottom of the well
Therefore, the depth of the well is
and the correct answer is B.
Survival of the fittest they are able to mature and reproduce because of their advantageous qualities
Zeros between a decimal point and a non zero number are insignificant.
Answer: 9.8N
Explanation: The velocity of a sound wave (v), tension on the string (T) and mass per unit length (u) are all related by the formulae below
T = v² * u
Where T is tension in Newton (N), v is velocity of sound waves in meter per seconds (m/s) and u is mass per unit length in kilogram per meter (kg/m)
u = mass of chord / length of chord
u = 0.44/ 8.1
u = 0.1 kg/m
Velocity of sound waves (v) =length of chord / time taken for wave to travel
v = 8.1 / 0.82 = 9.9m/s
Tension is calculated below using the formula
T = v² * u
T = (9.9)² x 0.1
T= 9.8N