Skip to main content
Ch. 7 - Logarithmic, Exponential Functions, and Hyperbolic Functions
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
All textbooksBriggs 3rd EditionCh. 7 - Logarithmic, Exponential Functions, and Hyperbolic FunctionsProblem 7.3.97a
Chapter 7, Problem 7.3.97a

Terminal velocity Refer to Exercises 95 and 96.


a. Compute a jumper’s terminal velocity, which is defined as lim t → ∞ v(t) = lim t → ∞ √(mg/k) tanh (√(kg/m) t).

Verified step by step guidance
1
Identify the given velocity function: \(v(t) = \sqrt{\frac{mg}{k}} \tanh \left( \sqrt{\frac{kg}{m}} t \right)\), where \(m\) is mass, \(g\) is acceleration due to gravity, and \(k\) is a constant related to air resistance.
Recall the definition of terminal velocity as the limit of \(v(t)\) as time \(t\) approaches infinity: \(\lim_{t \to \infty} v(t)\).
Focus on the behavior of the hyperbolic tangent function \(\tanh(x)\) as \(x \to \infty\). Remember that \(\tanh(x)\) approaches 1 when \(x\) becomes very large.
Apply this limit to the velocity function: replace \(\tanh \left( \sqrt{\frac{kg}{m}} t \right)\) with 1 as \(t \to \infty\).
Conclude that the terminal velocity is \(\lim_{t \to \infty} v(t) = \sqrt{\frac{mg}{k}} \times 1 = \sqrt{\frac{mg}{k}}\).

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
5m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Limit of a Function as t Approaches Infinity

The limit of a function as t approaches infinity describes the behavior of the function as the input grows without bound. In this problem, evaluating lim t → ∞ v(t) helps find the steady-state velocity, known as terminal velocity, where acceleration ceases and velocity stabilizes.
Recommended video:
06:11
Limits of Rational Functions: Denominator = 0

Hyperbolic Tangent Function (tanh)

The hyperbolic tangent function, tanh(x), is a smooth, continuous function that approaches 1 as x approaches infinity and -1 as x approaches negative infinity. Understanding tanh's limiting behavior is crucial to simplifying the velocity expression for large time values.
Recommended video:
05:13
Slopes of Tangent Lines

Terminal Velocity in Physics

Terminal velocity is the constant speed an object reaches when the force of gravity is balanced by the drag force, resulting in zero net acceleration. Mathematically, it is the limit of the velocity function as time goes to infinity, representing the maximum velocity attainable during free fall.
Recommended video:
06:29
Derivatives Applied To Velocity
Related Practice
Textbook Question

Chemotherapy In an experimental study at Dartmouth College, mice with tumors were treated with the chemotherapeutic drug Cisplatin. Before treatment, the tumors consisted entirely of clonogenic cells that divide rapidly, causing the tumors to double in size every 2.9 days. Immediately after treatment, 99% of the cells in the tumor became quiescent cells which do not divide and lose 50% of their volume every 5.7 days. For a particular mouse, assume the tumor size is 0.5 cm³ at the time of treatment.

a. Find an exponential decay function V₁(t) that equals the total volume of the quiescent cells in the tumor t days after treatment.

47
views
Textbook Question

Zero net area Consider the function f(x) = (1 − x)/x

a. Are there numbers 0 < a < 1 such that ∫₁₋ₐ¹⁺ᵃ f(x) dx = 0?

34
views
Textbook Question

Velocity of falling body Refer to Exercise 95, which gives the position function for a falling body. Use m = 75 kg and k = 0.2.


a. Confirm that the BASE jumper’s velocity t seconds after jumping is v(t) = d'(t) = √(mg/k) tanh (√(kg/m) t).

40
views
Textbook Question

Shallow-water velocity equation

a. Confirm that the linear approximation to ƒ(x) = tanh x at a = 0 is L(x) = x.

47
views
Textbook Question

Evaluating hyperbolic functions Evaluate each expression without using a calculator or state that the value does not exist. Simplify answers as much as possible.


a. cosh 0

59
views
Textbook Question

Falling body When an object falling from rest encounters air resistance proportional to the square of its velocity, the distance it falls (in meters) after t seconds is given by d(t) = (m/k) ln (cosh (√(kg/m) t)), where m is the mass of the object in kilograms, g = 9.8 m/s² is the acceleration due to gravity, and k is a physical constant.


a. A BASE jumper (m = 75 kg) leaps from a tall cliff and performs a ten-second delay (she free-falls for 10 s and then opens her chute). How far does she fall in 10 s? Assume k = 0.2.

54
views