"b. The nucleus is made of
protons and neutrons and has a positive charge" is the only option that is true about the atomic nucleus. The protons give it a positive charge.
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Answer:</h2>
Motor
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Explanation:</h2>
A motor is a machine that converts electrical energy into mechanical energy. In motors, electric energy is converted into mechanic energy when a magnetic torque acts on a conductor that carries a current. There are different types of motors like DC and AC motors. The moving part of a motor is called the rotor while the stationary part is called stator
Answer:

Explanation:
The volume of the balloon can be find compared the force in each cases so:
reduce 25% from 74kg

So the net force uproad on the balloon is

Now the density of the both gases air and helium are different however the volume is the same change offcorss the mass so:






Explanation:
It is given that,
When a high-energy proton or pion traveling near the speed of light collides with a nucleus, 
Speed of light, 
Let t is the time interval required for the strong interaction to occur. The speed is given by :




So, the time interval required for the strong interaction to occur is
. Hence, this is the required solution.