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Skydiving A skydiver is equipped with a stopwatch and an altimeter. As shown in Figure 3.2.7, he opens his parachuteseconds after exiting a plane flying at an altitude offeet and observes that his altitude isfeet. Assume that air resistance is proportional to the square of the instantaneous velocity, his initial velocity on leaving the plane is zero, and.

(a) Find the distance, measured from the plane, the skydiver has travelled during freefall in time.

[Hint: The constant of proportionalityin the model given in Problem 15 is not specified. Use the expression for terminal velocityobtained in part (b) of Problem 15 to eliminatefrom the IVP. Then eventually solve for.

(b) How far does the skydiver fall and what is his velocity at ?

Short Answer

Expert verified

Answer:

The distance measured from the plane isand

Step by step solution

01

Define velocity 

It is the pace at which an object's position changes in relation to a frame of reference and time. It may sound difficult, but velocity simply refers to the rate at which something moves in a given direction. It is a vector quantity, which implies that to define velocity, we require both magnitude (speed) and direction.

02

A variable separable differential equation can be solved using the following ways


03

Determination of velocity as a function of time


04

Determination of velocity as a function of time upon further substitution of values

We have,

Substituting the value of, we get

Applying the condition, we get

05

Using the variable separable method and calculating distance as a function of time


Now applying the conditionseconds), we get

06

Apply the point of condition to get the distance function


Applyingseconds), we get

Substituting the value of, we get

07

Substitute  to get the required distance


The velocity afteris

The velocity at the skydiver's fall

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Most popular questions from this chapter

Evaporating Raindrop As a raindrop falls, it evaporates while retaining its spherical shape. If we make the further assumptions that the rate at which the raindrop evaporates is proportional to its surface area and that air resistance is

negligible, then a model for the velocity v(t)of the raindrop is

dvdt+3(kฯ)(kฯ)t+r0v=g

Hereฯis the density of water,r0is the radius of the raindrop att=0,k<0 is the constant of proportionality, and the downward direction is taken to be the positive direction.

(a) Solve for v(t) if the raindrop falls from rest.

(b) Reread Problem 36 of Exercises 1.3 and then show that the radius of the raindrop at time t is r(t)=(kฯ)t+r0

(c) Ifr0=0.01ft andr=0.007ft10secondsafter the raindrop falls from a cloud, determine the time at which the raindrop has evaporated completely.

Solve Problem 9 ifgrams of chemicalis present initially. At what time is the chemicalhalf-formed?

When all the curves in a familyG(x,y,c1)=0 intersect orthogonally all the curves in another family localid="1667974378968" H(x,y,c1)=0, the families are said to be orthogonal trajectories of each other. See Figure 3.R.5. If localid="1667974383247" dydx=f(x,y) is the differential equation of one family, then the differential equation for the orthogonal trajectories of this family is localid="1667974387852" dydx=1f(x,y).Find the differential equation of the given family by computing localid="1667974392147" dydx and eliminating localid="1667974397114" c1from this equation. Then find the orthogonal trajectories of the family. Use a graphing utility to graph both families on the same set of coordinate axes.

y=c1x

When a vertical beam of light passes through a transparent medium, the rate at which its intensity Idecreases is proportional toI(t), where trepresents the thickness of the medium (in feet).In clear seawater, the intensity 3feet below the surface is 25% of the initial intensityI0of the incident beam. What is the intensity of the beam 15feet below the surface?

Question: Sawing Wood A long uniform piece of wood (cross sections are the same) is cut through perpendicular to its length by a vertical saw blade. See Figure 3.R.6. If the friction between the sides of the saw blade and the wood through which the blade passes is ignored, then it can be assumed that the rate at which the saw blade moves through the piece of wood is inversely proportional to the width of the wood in contact with its cutting edge. As the blade advances through the wood (moving, say, left to right) the width of a cross section changes as a nonnegative continuous function\(w\). If a cross section of the wood is described as a region in the\(xy\)-plane defined over an interval \((a,b)\)then, as shown in Figure 3.R.6(c), the position\(x\)of the saw blade is a function of time \(t\)and the vertical cut made by the blade can be represented by a vertical line segment. The length of this vertical line is the width\(w(x)\)of the wood at that point. Thus the position\(x(t)\)of the saw blade and the rate \(dx/dt\)at which it moves to the right are related to\(w(x)\)by\(w(x)\frac{{dx}}{{dt}} = k,x(0) = a\)

Here\(k\) represents the number of square units of the material removed by the saw blade per unit time.

  1. Suppose the saw is computerized and can be programmed so that\(k = 1\). Find an implicit solution of the foregoing initial-value problem when the piece of wood is a circular\(\log \). Assume a cross section is a circle of radius 2 centered at\((0,0)\) (Hint: To save time see formula 41 in the table of integrals given on the right inside page of the front cover.)
  2. Solve the implicit solution obtained in part (b) for time\(t\)as a function of\(x\). Graph the function\(t(x)\). With the aid of the graph, approximate the time that it takes the saw to cut through this piece of wood. Then find the exact value of this time.
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