<< Chapter < Page Chapter >> Page >

One application that helps illustrate the Mean Value Theorem involves velocity. For example, suppose we drive a car for 1 h down a straight road with an average velocity of 45 mph. Let s ( t ) and v ( t ) denote the position and velocity of the car, respectively, for 0 t 1 h. Assuming that the position function s ( t ) is differentiable, we can apply the Mean Value Theorem to conclude that, at some time c ( 0 , 1 ) , the speed of the car was exactly

v ( c ) = s ( c ) = s ( 1 ) s ( 0 ) 1 0 = 45 mph .

Mean value theorem and velocity

If a rock is dropped from a height of 100 ft, its position t seconds after it is dropped until it hits the ground is given by the function s ( t ) = −16 t 2 + 100 .

  1. Determine how long it takes before the rock hits the ground.
  2. Find the average velocity v avg of the rock for when the rock is released and the rock hits the ground.
  3. Find the time t guaranteed by the Mean Value Theorem when the instantaneous velocity of the rock is v avg .
  1. When the rock hits the ground, its position is s ( t ) = 0 . Solving the equation −16 t 2 + 100 = 0 for t , we find that t = ± 5 2 sec . Since we are only considering t 0 , the ball will hit the ground 5 2 sec after it is dropped.
  2. The average velocity is given by
    v avg = s ( 5 / 2 ) s ( 0 ) 5 / 2 0 = 1 100 5 / 2 = −40 ft/sec .
  3. The instantaneous velocity is given by the derivative of the position function. Therefore, we need to find a time t such that v ( t ) = s ( t ) = v avg = −40 ft/sec . Since s ( t ) is continuous over the interval [ 0 , 5 / 2 ] and differentiable over the interval ( 0 , 5 / 2 ) , by the Mean Value Theorem, there is guaranteed to be a point c ( 0 , 5 / 2 ) such that
    s ( c ) = s ( 5 / 2 ) s ( 0 ) 5 / 2 0 = −40 .

    Taking the derivative of the position function s ( t ) , we find that s ( t ) = −32 t . Therefore, the equation reduces to s ( c ) = −32 c = −40 . Solving this equation for c , we have c = 5 4 . Therefore, 5 4 sec after the rock is dropped, the instantaneous velocity equals the average velocity of the rock during its free fall: −40 ft/sec.
    The function s(t) = −16t2 + 100 is graphed from (0, 100) to (5/2, 0). There is a secant line drawn from (0, 100) to (5/2, 0). At the point corresponding to x = 5/4, there is a tangent line that is drawn, and this line is parallel to the secant line.
    At time t = 5 / 4 sec, the velocity of the rock is equal to its average velocity from the time it is dropped until it hits the ground.
Got questions? Get instant answers now!
Got questions? Get instant answers now!

Suppose a ball is dropped from a height of 200 ft. Its position at time t is s ( t ) = −16 t 2 + 200 . Find the time t when the instantaneous velocity of the ball equals its average velocity.

5 2 2 sec

Got questions? Get instant answers now!

Corollaries of the mean value theorem

Let’s now look at three corollaries of the Mean Value Theorem. These results have important consequences, which we use in upcoming sections.

At this point, we know the derivative of any constant function is zero. The Mean Value Theorem allows us to conclude that the converse is also true. In particular, if f ( x ) = 0 for all x in some interval I , then f ( x ) is constant over that interval. This result may seem intuitively obvious, but it has important implications that are not obvious, and we discuss them shortly.

Corollary 1: functions with a derivative of zero

Let f be differentiable over an interval I . If f ( x ) = 0 for all x I , then f ( x ) = constant for all x I .

Proof

Since f is differentiable over I , f must be continuous over I . Suppose f ( x ) is not constant for all x in I . Then there exist a , b I , where a b and f ( a ) f ( b ) . Choose the notation so that a < b . Therefore,

Questions & Answers

how does Neisseria cause meningitis
Nyibol Reply
what is microbiologist
Muhammad Reply
what is errata
Muhammad
is the branch of biology that deals with the study of microorganisms.
Ntefuni Reply
What is microbiology
Mercy Reply
studies of microbes
Louisiaste
when we takee the specimen which lumbar,spin,
Ziyad Reply
How bacteria create energy to survive?
Muhamad Reply
Bacteria doesn't produce energy they are dependent upon their substrate in case of lack of nutrients they are able to make spores which helps them to sustain in harsh environments
_Adnan
But not all bacteria make spores, l mean Eukaryotic cells have Mitochondria which acts as powerhouse for them, since bacteria don't have it, what is the substitution for it?
Muhamad
they make spores
Louisiaste
what is sporadic nd endemic, epidemic
Aminu Reply
the significance of food webs for disease transmission
Abreham
food webs brings about an infection as an individual depends on number of diseased foods or carriers dully.
Mark
explain assimilatory nitrate reduction
Esinniobiwa Reply
Assimilatory nitrate reduction is a process that occurs in some microorganisms, such as bacteria and archaea, in which nitrate (NO3-) is reduced to nitrite (NO2-), and then further reduced to ammonia (NH3).
Elkana
This process is called assimilatory nitrate reduction because the nitrogen that is produced is incorporated in the cells of microorganisms where it can be used in the synthesis of amino acids and other nitrogen products
Elkana
Examples of thermophilic organisms
Shu Reply
Give Examples of thermophilic organisms
Shu
advantages of normal Flora to the host
Micheal Reply
Prevent foreign microbes to the host
Abubakar
they provide healthier benefits to their hosts
ayesha
They are friends to host only when Host immune system is strong and become enemies when the host immune system is weakened . very bad relationship!
Mark
what is cell
faisal Reply
cell is the smallest unit of life
Fauziya
cell is the smallest unit of life
Akanni
ok
Innocent
cell is the structural and functional unit of life
Hasan
is the fundamental units of Life
Musa
what are emergency diseases
Micheal Reply
There are nothing like emergency disease but there are some common medical emergency which can occur simultaneously like Bleeding,heart attack,Breathing difficulties,severe pain heart stock.Hope you will get my point .Have a nice day ❣️
_Adnan
define infection ,prevention and control
Innocent
I think infection prevention and control is the avoidance of all things we do that gives out break of infections and promotion of health practices that promote life
Lubega
Heyy Lubega hussein where are u from?
_Adnan
en français
Adama
which site have a normal flora
ESTHER Reply
Many sites of the body have it Skin Nasal cavity Oral cavity Gastro intestinal tract
Safaa
skin
Asiina
skin,Oral,Nasal,GIt
Sadik
How can Commensal can Bacteria change into pathogen?
Sadik
How can Commensal Bacteria change into pathogen?
Sadik
all
Tesfaye
by fussion
Asiina
what are the advantages of normal Flora to the host
Micheal
what are the ways of control and prevention of nosocomial infection in the hospital
Micheal
what is inflammation
Shelly Reply
part of a tissue or an organ being wounded or bruised.
Wilfred
what term is used to name and classify microorganisms?
Micheal Reply
Binomial nomenclature
adeolu
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 2

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Calculus volume 1. OpenStax CNX. Feb 05, 2016 Download for free at http://cnx.org/content/col11964/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Calculus volume 1' conversation and receive update notifications?

Ask