Answer and Explanation:
a. An oxygen-filled balloon is not able to float in the air, because the oxygen inside the balloon is of the same density, that is, the same "weight" as the oxygen outside the balloon and present in the atmosphere. The balloon can only float if the gas inside it is less dense than atmospheric oxygen. Helium gas is less dense than atmospheric gas, so if a balloon is filled with helium gas, that balloon will be able to float because of the difference in density.
b. The ship is able to float in the water because its steel construction is hollow and full of air. This makes the average density of this ship less than the density of water, which makes the ship lighter than water and for this reason, this ship is able to float. In addition, the ship is partially immersed, allowing the weight of the ship on the water to counteract the buoyant force that the water promotes on the ship. Weight and buoyant are two opposing forces that keep the ship afloat.
Can you translate to english ?
Answer:
The kinetic energy is 
Explanation:
From the question we are told that
The potential difference is 
The potential energy of the end is mathematically represented as

q is the charge on an electron with a constant value of 
substituting values


Now from the law of energy conservation
The 
Where
is the potential energy at the end
So

The negative sign is not includes because kinetic energy can not be negative
The distance covered by Arthur is
3t
The distance covered by Betty from where Arthur started is
100 - 2t
They meet each other when this distance is equal
3t = 100 - 2t
t = 20 s
Since the dog has a constant speed of 5m/s, the distance that Spot has run is
5 m/s (20s) = 100 m