The speed of the 0.8 kg ball immediately after collision is 0.625 m/s in opposite direction to the stationary ball.
The given parameters;
- mass of the ball, m₁ = 0.8 kg
- speed of the ball, u₁ = 2.5 m/s
- mass of the object at rest, m₂ = 2.5 kg
- final velocity of the object at rest, v₂ = 1 m/s
Let the final velocity of the 0.8 kg ball immediately after collision = v₁
Apply the principle of conservation of linear momentum;
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂
(0.8 x 2.5) + (2.5 x 0) = (0.8)v₁ + 2.5(1)
2 = 2.5 + (0.8)v₁
-0.5 = (0.8)v₁

Thus, the speed of the 0.8 kg ball immediately after collision is 0.625 m/s in opposite direction to the stationary ball.
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If you look on the periodic table you will see the top group elements depending on how the elements relate to each in the column. All of the elements in that column show they all have 1 electron in their valence shell. Some of the chemicals in that family or group are Sodium, Lithium, Potassium. The are very reactive because they only have one electron and what 7 more to become stable.
That is a lunar eclipse. At night, when the Earth is between the Sun and the moon, the moon would appear to be red. Just for future reference, a solar eclipse is when the Moon is between the Sun and Earth. Speaking of which, check out the solar eclipse this August!
Endoskeleton- an internal skeleton, such as the bony or cartilaginous skeleton of vertebrates.
Exoskeleton- a rigid external covering for the body in some invertebrates animals, especially Arthropods, providing both support and protection.
That would be reflection.