According to the law of conservation of momentum:

m1 = mass of first object
m2 = mass of second object
v1 = Velocity of the first object before the collision
v2 = Velocity of the second object before the collision
v'1 = Velocity of the first object after the collision
v'2 = Velocity of the second object after the collision
Now how do you solve for the velocity of the second car after the collision? First thing you do is get your given and fill in what you know in the equation and solve for what you do not know.
m1 = 125 kg v1 = 12m/s v'1 = -12.5m/s
m2 = 235kg v2 = -13m/s v'2 = ?




Transpose everything on the side of the unknown to isolate the unknown. Do not forget to do the opposite operation.




The velocity of the 2nd car after the collision is
0.03m/s.
The density of seawater at a depth where the pressure is 500 atm is 
Explanation:
The relationship between bulk modulus and pressure is the following:

where
B is the bulk modulus
is the density at surface
is the variation of pressure
is the variation of density
In this problem, we have:
is the bulk modulus

is the change in pressure with respect to the surface (the pressure at the surface is 1 atm)
Therefore, we can find the density of the water where the pressure is 500 atm as follows:

Learn more about pressure in a fluid:
brainly.com/question/9805263
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