Base on my research, within 2 hours you have a number of atoms which remain.
N= N0*2^(-t/6.020 = N= N0*2^-0.33223= 07943 N0
So, the number of atoms that are being disintegrated is N0-N=N0*(1-0.79430)=0.2057 N0
It must be equal to 15 mCi = 15*3.7*10^7= 5.55*10^8 atoms
N0= 5.55*10*8/0.2057 = 2.698*10^9 atoms
Therefore, 2.698*10^9 atoms is the number of N0
Answer:OBSERVING IS WHATCHING A OBJECT VERY CLOSELY AND EXPIERIMENTING IS WER YOUTEST ON A CERTAIN THING OR CREATURE OR MASS OR ELEMENT
Explanation:IM THE MYSTERY MAN WHOOSH
Acceleration of the ball is 
Explanation:
The acceleration of the ball can be found by using Newton's second law of motion, which states that the net force acting on an object is equal to the product between the mass of the object and its acceleration:

where
F is the net force
m is the mass
a is the acceleration
For the ball in this problem, we have
m = 0.50 kg (mass)
F = 25 N (force)
thereofre, the acceleration of the ball is

Learn more about Newton's second law:
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Answer:
0.000234 seconds
Explanation:
Since the row is 0.15m, its radius of rotation must be 0.15 / 2 = 0.075 m
We can start by calculating the angular speed of the rod:
Since one revolution equals to 2π rad. The speed in revolution per second must be
26800 / 2π = 4265 revolution/s
The number of seconds per revolution, or period, is the inverse:
1/4265 = 0.000234 seconds