Hi! Some rocks are porous material, like a sponge, with lots of air pockets inside, so they can absorbe water. In this case, the water level dropped 5.65m because tha volume of water went inside the rock filling the air pockets. The water replaced the air, that flowed to the outside water as bubbles and then to the air above the water.
First we can say that since there is no external force on this system so momentum is always conserved.




now by the condition of elastic collision
![v_{2f} - v_{1f} = 0.8 - 0[\tex]now add two equations[tex]3*v_{2f} = 1.6](https://tex.z-dn.net/?f=v_%7B2f%7D%20-%20v_%7B1f%7D%20%3D%200.8%20-%200%5B%5Ctex%5D%3C%2Fp%3E%3Cp%3Enow%20add%20two%20equations%3C%2Fp%3E%3Cp%3E%5Btex%5D3%2Av_%7B2f%7D%20%3D%201.6)

also from above equation we have

So ball of mass 0.6 kg will rebound back with speed 0.267 m/s and ball of mass 1.2 kg will go forwards with speed 0.533 m/s.
Acceleration is change in velocity over time --> 
Δv or change in velocity equals the Final velocity minus the initial velocity
Our initial velocity here is 60m/s while our final velocity is 0 m/s
The time interval is 85 seconds so...



The negative is there to indicate that the train in slowing down or decelerating
Answer:



Explanation:
= Permittivity of free space = 
= Vacuum permeability = 
E = Electric field = 57.5 V/m
c = Speed of light = 
Magnetic field is given by

The magnetic field strength is 
Energy density is given by

The energy density is 
Power flow per unit area is given by

Power flow per unit area is 