Asample contains 36g of a radioactive isotope. how much radioactive isotope remains in the sample after 3 half-lives

4.5 g

Explanation:

N0 = 36 g, Let half life is T.

t = 3 T, n is number of half lives = t / T = 3

By using the decay law of radioactivity

N / N0 = (1 / 2)^n

where, N0 be the initial amount

N be the amount left

n be the number of half lives

N / 36 = (1/2)^3

N / 36 = 1 / 8

N = 36 / 8 = 4.5 g

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered