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.  

prolly a beacuse the momentuem the car has increases while going down hill