Answer: 71.72 days
Explanation:
This problem can be solved using the <u>Radioactive Half Life Formula: </u>
(1)
Where:
is the final amount of Iodine-131
is the initial amount of Iodine-131
is the time elapsed
is the half life of Iodine-131
Knowing this, let's substitute the values and find
from (1):
(2)
(3)
Applying natural logarithm in both sides:
(4)
(5)
Finding
:
Answer:
Part a)

Part b)

Part c)

Explanation:
Part a)
As we know that the friction force on two boxes is given as



Now we know by Newton's II law

so we have




Part b)
For block B we know that net force on it will push it forward with same acceleration so we have




Part c)
If Alex push from other side then also the acceleration will be same
So for box B we can say that Net force is given as




Is there any possible chance that at some point in your science
studies, sometime before you were given this question for your
homework, that maybe you might have encountered this formula
for the period of a simple pendulum ?
Period = (2 pi) √(length/gravity) .
If the length is 0.23 meter, and the
acceleration of gravity is 9.8 m/s²,
then the period is
= (2 pi) √(0.23/9.8)
= 0.963... second (rounded)
That's how long it takes for a simple pendulum, 23cm long,
hanging on a massless string and not swinging too far to
the side, to complete one full swing left and right.
Now, if you can figure out how many periods of 0.963 second
there are in 30 seconds, you'll have your answer. I'll leave
that part of it to you.
<span>I am pretty sure the correct answer is C.
It makes the most sense.
Please correct me if I'm wrong.</span>