# NEED HELP WITH CALC

Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.)
Answer: P(t) = (b) Estimate the half-life of strontium.
Hint: Use your graphing calculator and the trace function. (Or use natural logarithms as in 1.9).(c) If presently there is 5.5 grams of strontium, estimate how many grams of the substance will remain after 11 years.

1. 👍 1
2. 👎 0
3. 👁 1,502
1. Yes, you do

ds/dt = -.02 s

ds/s = -.02 dt

ln s = -.02 t + c

e^ln s = s = e^(c-.02t) = e^c e^-.02 t

e^c = C any old constant in the general solution

s = C e^-.02 t
when t = 0, s = Si the initial amount
so
s/Si = e^-.02 t
BUT that is P, the fraction remaining so we have part a

b) .5 = e^-.02 t
ln .5 = -.02 t = -.693
t = 34.7 years half life

in 11 years
s = 5.5 e^-.02*11
s = 4.41

1. 👍 0
2. 👎 2
posted by Damon

## Similar Questions

1. ### Calculus

Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t)=?

asked by Anonymous on January 28, 2018
2. ### math

Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t)=(.98)^t (b)

asked by mac on September 14, 2017
3. ### Math

Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t) = (b) Estimate the

asked by Anonymous on June 27, 2014
4. ### calculus

Suppose strontium-90 decays at a rate of 2 percent per year. (a) Write the fraction P of strontium remaining, as function of t, measured in years. (Assume that at time t=0 there is 100 % remaining.) Answer: P(t) = (b) Estimate the

asked by Anonymous on June 27, 2014
5. ### Chemistry

Radioactive decay is first order in the decaying isotope. For example, strontium-90 contained in fallout from nuclear explosions decays to yttrium-90 and a beta particle. Write the rate law for the decay of strontium-90. Can you

asked by Soco on August 7, 2015
1. ### FINANCE

8. Suppose that the current one-year rate (one-year spot rate) and expected one-year T-bill rates over the following three years (i.e., years 2, 3, and 4, respectively) are as follows: 1R1 = 5 percent, E(2r1) = 6 percent, E(3r1) =

asked by Dashawn on October 31, 2014
2. ### Math algebra

The radioactive decay of a substance is expressed by A=A^0 e^ -kt, where the initial amount A^0, decays to an amount A after t years. The positive constant k differs for each substance. Strontium 90 decays such that k=.028. Find

asked by Emily on December 15, 2016
3. ### FINANCE

8. Suppose that the current one-year rate (one-year spot rate) and expected one-year T-bill rates over the following three years (i.e., years 2, 3, and 4, respectively) are as follows: 1R1 = 5 percent, E(2r1) = 6 percent, E(3r1) =

asked by Anonymous on October 31, 2014
4. ### math

The radioactive decay of a substance is expressed by A=A^0 e^ -kt, where the initial amount A^0, decays to an amount A after t years. The positive constant k differs for each substance. Strontium 90 decays such that k=.028. Find

asked by sara on December 1, 2016
5. ### chemistry

Strontium-90 decays through the emission of beta particles. It has a half-life of 29 years. How long does it take for 80% of a sample of strontium-90 to decay? Show process of how you got this

asked by Urgent Help on January 10, 2013

More Similar Questions