<span>3.2 grams
The first thing to do is calculate how many half lives have expired. So take the time of 72 seconds and divide by the length of a half life which is 38 seconds. So
72 / 38 = 1.894736842
So we're over 1 half life, but not quite 2 half lives. So you'll have something less than 12/2 = 6 grams, but more than 12/4 = 3 grams.
The exact answer is done by dividing 12 by 2 raised to the power of 1.8947. So let's calculate 2^1.8947 power
= 12 g / (e ^ ln(2)*1.8947)
= 12 g / (e ^ 0.693147181 * 1.8947)
= 12 g / (e ^ 1.313305964)
= 12 g / 3.718446464
= 3.227154167 g
So rounded to 2 significant figures gives 3.2 grams.</span>
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As per impulse momentum theorem we know that

now here we will have

t = 1.30 ms
m = 0.144 kg

now we need to find final speed using above formula


so final speed is given as above
The velocity of an electron that has been accelerated through a difference of potential of 100 volts will be 5.93 *
m/s
Electrons move because they get pushed by some external force. There are several energy sources that can force electrons to move. Voltage is the amount of push or pressure that is being applied to the electrons.
By conservation of energy, the kinetic energy has to equal the change in potential energy, so KE=q*V. The energy of the electron in electron-volts is numerically the same as the voltage between the plates.
given
charge of electron = 1.6 ×
C
mass of electron = 9.1 ×
kg
Force in an electric field = q*E
potential energy is stored in the form of work done
potential energy = work done = Force * displacement
= q * (E * d)
= q * (V) = 1.6 ×
* 100
stored potential energy = kinetic energy in electric field
kinetic energy = 1/2 * m * 
= 1/2 * 9.1 ×
* 
equation both the equations
1/2 * 9.1 ×
*
= 1.6 ×
= 0.352 *
m/s
= 35.2 * 
= 5.93 *
m/s
To learn more about kinetic energy in electric field here
brainly.com/question/8666051
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Bubbles came off from the copper pennies are hydrogen gas. There many free hydrogen ions in an acid like vinegar. And because of the chemical reaction between the copper and the vinegar, many hydrogen ions joined together to form hydrogen gas.