Lead-202 has a half-life of 53,000 years. how long will it take for 15/16 of a sample of lead-202 to decay?

a) 106,000 years

b) 159,000 years

c) 212,000 years

d) 265,000 years

C) 212,000 years

Explanation:

The half-life of a radioactive sample is the time it takes for half of the sample to decay.

In this case, the half-life is 53,000 years: this means that after 53,000 years, half of the sample will decay. So we will have:

- After 1 half life (53,000 years): 1/2 of the sample has decayed, so 1/2 is left undecayed

- After 2 half-lives (106,000 years): since the amount left is now 1/2, the amount that decay now is . So the total amount decayed is now , and the amount left is

- After 3 half-lives (159,000 years): since the amount left is now 1/4, the amount that decay now is . So the total amount decayed is now , and the amount left is

- After 4 half-lives (212,000 years): since the amount left is now 1/8, the amount that decay now is . So the total amount decayed is now , and the amount left is

So, the correct answer is

C) 212,000 years

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.