Physics, 20.08.2019 20:30, BreBreDoeCCx

The half-life of a certain element is 100 days. how many half-lives will it be before only one-eighth of this element remains?
2
3
8
12.5

Answers: 2

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answered: mathman783

Explanation:

The half-life is the time it takes for the amount of radioactive isotope to halve. Therefore, we have:

- After 1 half-life, only 1/2 of the element will be left

- After 2 half-lives, only 1/4 of the element will be left

- After 3 half-lives, only 1/8 of the element will be left

So, it will take 3 half-lives for the element to become 1/8 of its original amount.

Mathematically, this can be also verified by using the equation

$\frac{N(t)}{N_0}=(\frac{1}{2})^\frac{t}{\tau_{1/2}}$

where

N(t) is the amount of the element left at time t

N0 is the initial amount of the element

$\tau_{1/2}$ is the half-life

Substituting $t=3\tau_{1/2}$ (3 half-lives), we find

$\frac{N(t)}{N_0}=(\frac{1}{2})^3=\frac{1}{8}$

answered: Guest

this isn't the answer but they're the graphs

answered: Guest

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

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The half-life of a certain element is 100 days. how many half-lives will it be before only one-eight...