Suppose the half-life of element k is 20 minutes. if you have a 200 g sample of k, how much of element k will be left after 60 minutes? (do not use significant digits in answering this question).

25 grams

Explanation:

Radioactive decay follows first order kinetics.

Half-life of element = 20 minutes

N = amount left after time t = ?

= initial amount  = 200 g

= rate constant

t= time  = 60 min

Thus amount left after 60 minutes will be 25 grams.

what is the average time it took the car to travel 0.25 meters?

⇒ 2.23 seconds

what is the average time it took the car to travel 0.50 meters?

⇒ 3.13 seconds