Arobber dropped a bag of loot into a 30 m well. if the speed of sound is 340 m/s how long after dropping the bag does he hear the splash?

First we have to determine the time for the bag fall by the kinematic equation,

Here, u is initial velocity which is zero, g is acceleration due to gravity its value is 9.8 m/s2 and s is displacement and its value is given 30 m.

Therefore,

As  sound travels at 340 m/s, so the time for the sound to travel back up the well,

Thus , the splash is heard at .

Therefore, splash is heard about 2.55 s after the bag is dropped.  

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j