1. I think it's the trails left by an electron as it moves around the nucleus.
2. The atomic number is the number of protons so it is 8.
3. It's mass is lowered but it is still the same element.
Answer:
a physical change
Explanation:
after the water turns to ice, it will melt and became water again making which means it's reversible this being. a physical change
Answer:

Explanation:
From the question we are told that:
Bowling ball Speed 
Beach ball Speed 
Let The Mass be equal i.e

Therefore
Generally the equation for Velocity of beach ball after collision
is mathematically given by
Since Velocity is Vector Quantity
Therefore



The radius of the sphere in meters is ,r =
Think about the angle the ground and the shadow make. Since the sun's beams are parallel, the angle created by the stick's shadow is also equal. Since the stick is 1 m high and its shadow is 2 m long, we know that the stick's angle is arctan 1/2. Therefore, by thinking of a right-angled triangle,
r/10 = tan [arctan(1/2)] = tan (1/2)
Since, tan (θ/2) = 1-cos(θ) / sin(θ)
we find that,
r/10 = 
Hence, r = 
So, the radius of the sphere in meters is ,r =
Learn more about radius (r) of the sphere here;
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