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Consider this parabola: The minimum occurs at (x,y)=(0.99,0.86), and y = 4.99 at

ID: 2126077 • Letter: C

Question

Consider this parabola: The minimum occurs at (x,y)=(0.99,0.86), and y = 4.99 at x = 1.65. Determine the rate of change of y with respect to x, at the point x = 3.20.


Let F(s)=(a2+(b2+s2)1/2)1/2 where a and b are constants.
(A) Calculate F'(a).
[Hint: F'(s) means dF/ds.]
[Data: a = 1.8; b = 1.7.]

(B) Calculate F'(b).


Consider the oscillatory function g(t)=A sin(?t), where A = 3.38 and ? =1.20. Show that d2g/dt2 = ? K g and calculate K.


Consider the oscillatory function g(t)=A cos(?t + ?) where A, ? and ? are constants.
Calculate (1/2) (dg/dt)2+(?2/2) (g)2, at some arbitrary value of t.
[Data: A=2.50, ? = 1.98, ? = 2.03.]

As a planet revolves around the sun, the distance from the sun, as a function of the angular position ?, is given by the function
r(?) = ? / [ 1+? cos(???0) ].
Calculate the perihelion and aphelion distances.
[Data: ? = 4.9, ? = 0.019, ?0 = 2.8.]


A function H(?) has the property that
[H(?)]2+[H?(?)]2 = C is constant, i.e., independent of the variable ?. Determine the function H(?), with H(0)=0. Evaluate H(?/4) if C = 1.3.


Given these parametric equations:
r(?)=?[ 1 + e cosh? ] and t(?)=T [ ?+ e sinh? ],
with ? = 1.8, T = 4.7, e = 1.6.
Calculate dr/dt as a function of r. Evaluate dr/dt at r = ?(1+e), and in the limit as r tends to infinity.


A quantity Q increases exponentially as a function of time t;
Q(t)=Q0 exp(?t).
Here Q0 is the value of the quantity at t=0; and ? = 1.1.
(A) Find the time when Q = 10 Q0.

(B) Find the time when Q = 100 Q0.

(C) Show that dQ/dt is proportional to Q, and determine the constant of proportionality.



Carbon Dating. When a plant is alive, it has a constant concentration of the isotope C-14 (compared to other isotopes of carbon) obtained from the atmosphere in carbon dioxide. But C-14 is radioactive, with half-life ? = 5730  years. After the plant dies, the concentration of C-14 decays exponentially in time,
C14(t) = C14(0) (1/2)t/?

(A) If an archeological sample of organic material has C14 = 0.01 C14(0), what is the age of the sample (i.e., the time that has passed since the material was in a living plant)?

(B) Show that dC14/dt = ? ?C14 and calculate the value of ?


A quantity q depends on a variable r. If r = 0 then q = 1. The rate of change of q(r) with respect to r is 5 q(r). Determine q(r). Calculate q(1.32).


Jack and the Beanstalk. Suppose Jack's bean produced a seedling (1 inch tall) that grew 1 inch for every inch of existing plant, per hour. How long did it take for the plant to grow from 1 inch tall to 50 feet tall?

Explanation / Answer

ow that we have an expression for the current, we can find the maximumvalue of the current by setting the first derivative of the current to zero and solving for t: di d -=-(te-at)= e-at+ t( -a)eat = (1- at)e-at = 0 dt dt Since e-at never equals 0 for a finite value of t, the expression equals 0 onlywhen (1- at)= 0. Thus, t = 1/a will cause the current to be maximum. Forthis value of t, the current is