<h2>
Answer: The half-life of beryllium-15 is 400 times greater than the half-life of beryllium-13.</h2>
Explanation:
The half-life 
of a radioactive isotope refers to its decay period, which is the average lifetime of an atom before it disintegrates.
In this case, we are given the half life of two elements:
beryllium-13: 
beryllium-15: 
As we can see, the half-life of beryllium-15 is greater than the half-life of beryllium-13, but how great?
We can find it out by the following expression:
Where 
is the amount we want to find:
Finally:
Therefore:
The half-life of beryllium-15 is <u>400 times greater than</u> the half-life of beryllium-13.
Answer:
Commutator is a ring which reverse the direction of current in AC circuit so that the coil connected to it will continuous to move in the same direction.
Explanation:
In motors there exist a coil which is rotated due to torque of magnetic field when current flow through it. Since AC current is used to run the motor so we know that AC current changes its direction after half cycle.
So here commutator plays an important role to reverse the direction of current after every half cycle so that the current goes in same direction always into the coil.
This will produce a constant direction torque on the coil so that it will rotate in same sense always.
So commutator role is to provide same direction current to the coil by reversing its direction after every half cycle
Answer:
helium-4 (90%) or tritium (7%).
Explanation:
hope it helped u buddy
The answer to this question is a) sulfur
Answer:
Without it, we could not survive on Earth. Earth orbits the sun due to the gravity of the sun, which maintains us at a convenient distance from it to enjoy the sun's warmth and light. It keeps the air we need to breathe and our atmosphere in place. Our planet is held together by gravity.
