How many times did the original sample lose 50% of its radioactivity ?
-- Start with. . . . . . . . . . . . 12 grams.
-- Lose half of it once. . . . . . 6 grams left.
-- Lose half of it again . . . . . 3 grams left.
-- Lose half of it again . . . . . 1.5 grams left.
-- Lose half of it again . . . . . 0.75 gram left.
-- How many times did it lose half ? 4 times.
-- How long does it take to lose half ? 4.5 days.
(That's why it's called the 'half-life'.)
-- How long did it take to lose half, 4 times ?
(4 x 4.5 days) = 18 days .
Cryptologist is not a scientist.
From 50km/h to 0km/h in 0.5s we need next acceleration:
First we convert km/h in m/s:
50km/h = 50*1000/3600=13.8888 m/s
a = v/t = 13.88888/0.5 = 27.77777 m/s^2
Now we use Newton's law:
F=m*a
F=1700*27.7777 = 47222N
Explanation:
power=f×v. recall= distances/ time
= f× d/t
= 30 × 2/5
=12watt
True is the anwser to your question
Hope this helps
