Let say the two train cars are of masses
and 
now if the speed of two cars are
and 
then we can say that the momentum of two cars before they collide is given by

here two cars are moving in opposite direction so we can say that the net momentum is subtraction of two cars momentum.
Now since in these two car motion there is no external force on them while they collide
So the momentum of two cars are always conserved.
hence we can say that the final momentum of two cars will be same after collision as it is before collision

Answer:
F(Mars) = 2 G m M / (4 R)^2 force of Sun on Mars
F(Merc) = G m M / R^2 force of force of Sun on Mercury
R = distance of Sun from Mercury, m = mass of Mercury
F(Merc) / F(Mars) = 4^2 / 2 = 8
Answer: A <u>Nebula </u>is left behind. A spectacular explosion in which a star ejects most of its mass in a violently expanding cloud of debris.
Hope this helps!
To solve this problem it is necessary to apply the concepts related to the Kinetic Energy and the Energy Produced by the heat loss. In mathematical terms kinetic energy can be described as:

Where,
m = Mass
v = Velocity
Replacing we have that the Total Kinetic Energy is



On the other hand the required Energy to heat up t melting point is


Where,
m = Mass
Specific Heat
Change at temperature
Latent heat of fussion
Heat required to heat up to melting point,




The energy required to melt is larger than the kinetic energy. Therefore the heat of fusion of lead would be 327 ° C: The melting point of lead.
For heating Solid, Liquid, Gas and for cooling the opposite Gas, Liquid, Solid