Answer:
The kinetic energy of the system after the collision is 9 J.
Explanation:
It is given that,
Mass of object 1, m₁ = 3 kg
Speed of object 1, v₁ = 2 m/s
Mass of object 2, m₂ = 6 kg
Speed of object 2, v₂ = -1 m/s (it is moving in left)
Since, the collision is elastic. The kinetic energy of the system before the collision is equal to the kinetic energy of the system after the collision. Let it is E. So,

E = 9 J
So, the kinetic energy of the system after the collision is 9 J. Hence, this is the required solution.
C. The water cycle spreads water out evenly around the whole Earth
Answer:
I think it is difficult to determine what has caused climate change in the distant past because it must have been a long time ago so geologists can't carry out different experiments and figure out what gases the planet had conjured, so geologists can only make predictions based off the evidence they currently have from what the planet looked like before. The planet must have changed over the years, therefore the climate has also changed in the future, so they cannot work with how the planet looked in the past.
Answer:
The gravitational force between them increases by a factor of 4
Explanation:
Gravitational force is a force of attraction between two objects with masses M and m which are separated by a distance R. It is given mathematically as:
Fg = GMm/R²
Where G = Gravitational constant.
If the distance between their centers, R, decreases by a factor of 2, then it means the new distance between their centers is:
r = R/2
Hence,the gravitational force becomes:
Fg = GMm/r²
Fg = GMm/(R/2)²
Fg = GMm/(R²/4)
Fg = 4GMm/R²
Hence,the gravitational force increases by a factor of 4.