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Find the equation of a tangent line to the curve of the function f ( x ) = 5 x 2 x + 4 at x = 2.

y = 19 x 16

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Finding the instantaneous speed of a particle

If a function measures position versus time, the derivative measures displacement versus time, or the speed of the object. A change in speed or direction relative to a change in time is known as velocity . The velocity at a given instant is known as instantaneous velocity .

In trying to find the speed or velocity of an object at a given instant, we seem to encounter a contradiction. We normally define speed as the distance traveled divided by the elapsed time. But in an instant, no distance is traveled, and no time elapses. How will we divide zero by zero? The use of a derivative solves this problem. A derivative allows us to say that even while the object’s velocity is constantly changing, it has a certain velocity at a given instant. That means that if the object traveled at that exact velocity for a unit of time, it would travel the specified distance.

Instantaneous velocity

Let the function s ( t ) represent the position of an object at time t . The instantaneous velocity    or velocity of the object at time t = a is given by

s ( a ) = lim h 0 s ( a + h ) s ( a ) h

Finding the instantaneous velocity

A ball is tossed upward from a height of 200 feet with an initial velocity of 36 ft/sec. If the height of the ball in feet after t seconds is given by s ( t ) = −16 t 2 + 36 t + 200 , find the instantaneous velocity of the ball at t = 2.

First, we must find the derivative s ( t ) . Then we evaluate the derivative at t = 2 , using s ( a + h ) = 16 ( a + h ) 2 + 36 ( a + h ) + 200 and s ( a ) = 16 a 2 + 36 a + 200.

s ( a ) = lim h 0 s ( a + h ) s ( a ) h          = lim h 0 16 ( a + h ) 2 + 36 ( a + h ) + 200 ( 16 a 2 + 36 a + 200 ) h          = lim h 0 16 ( a 2 + 2 a h + h 2 ) + 36 ( a + h ) + 200 ( 16 a 2 + 36 a + 200 ) h          = lim h 0 16 a 2 32 a h 16 h 2 + 36 a + 36 h + 200 + 16 a 2 36 a 200 h          = lim h 0 16 a 2 32 a h 16 h 2 + 36 a + 36 h + 200 + 16 a 2 36 a 200 h          = lim h 0 32 a h 16 h 2 + 36 h h          = lim h 0 h ( 32 a 16 h + 36 ) h          = lim h 0 ( 32 a 16 h + 36 )          = 32 a 16 0 + 36   s ( a ) = 32 a + 36   s ( 2 ) = 32 ( 2 ) + 36          = 28
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A fireworks rocket is shot upward out of a pit 12 ft below the ground at a velocity of 60 ft/sec. Its height in feet after t seconds is given by s = 16 t 2 + 60 t 12. What is its instantaneous velocity after 4 seconds?

–68 ft/sec, it is dropping back to Earth at a rate of 68 ft/s.

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Key equations

average rate of change AROC = f ( a + h ) f ( a ) h
derivative of a function f ( a ) = lim h 0 f ( a + h ) f ( a ) h

Key concepts

  • The slope of the secant line connecting two points is the average rate of change of the function between those points. See [link] .
  • The derivative, or instantaneous rate of change, is a measure of the slope of the curve of a function at a given point, or the slope of the line tangent to the curve at that point. See [link] , [link] , and [link] .
  • The difference quotient is the quotient in the formula for the instantaneous rate of change:
    f ( a + h ) f ( a ) h
  • Instantaneous rates of change can be used to find solutions to many real-world problems. See [link] .
  • The instantaneous rate of change can be found by observing the slope of a function at a point on a graph by drawing a line tangent to the function at that point. See [link] .
  • Instantaneous rates of change can be interpreted to describe real-world situations. See [link] and [link] .
  • Some functions are not differentiable at a point or points. See [link] .
  • The point-slope form of a line can be used to find the equation of a line tangent to the curve of a function. See [link] .
  • Velocity is a change in position relative to time. Instantaneous velocity describes the velocity of an object at a given instant. Average velocity describes the velocity maintained over an interval of time.
  • Using the derivative makes it possible to calculate instantaneous velocity even though there is no elapsed time. See [link] .

Questions & Answers

Three charges q_{1}=+3\mu C, q_{2}=+6\mu C and q_{3}=+8\mu C are located at (2,0)m (0,0)m and (0,3) coordinates respectively. Find the magnitude and direction acted upon q_{2} by the two other charges.Draw the correct graphical illustration of the problem above showing the direction of all forces.
Kate Reply
To solve this problem, we need to first find the net force acting on charge q_{2}. The magnitude of the force exerted by q_{1} on q_{2} is given by F=\frac{kq_{1}q_{2}}{r^{2}} where k is the Coulomb constant, q_{1} and q_{2} are the charges of the particles, and r is the distance between them.
Muhammed
What is the direction and net electric force on q_{1}= 5µC located at (0,4)r due to charges q_{2}=7mu located at (0,0)m and q_{3}=3\mu C located at (4,0)m?
Kate Reply
what is the change in momentum of a body?
Eunice Reply
what is a capacitor?
Raymond Reply
Capacitor is a separation of opposite charges using an insulator of very small dimension between them. Capacitor is used for allowing an AC (alternating current) to pass while a DC (direct current) is blocked.
Gautam
A motor travelling at 72km/m on sighting a stop sign applying the breaks such that under constant deaccelerate in the meters of 50 metres what is the magnitude of the accelerate
Maria Reply
please solve
Sharon
8m/s²
Aishat
What is Thermodynamics
Muordit
velocity can be 72 km/h in question. 72 km/h=20 m/s, v^2=2.a.x , 20^2=2.a.50, a=4 m/s^2.
Mehmet
A boat travels due east at a speed of 40meter per seconds across a river flowing due south at 30meter per seconds. what is the resultant speed of the boat
Saheed Reply
50 m/s due south east
Someone
which has a higher temperature, 1cup of boiling water or 1teapot of boiling water which can transfer more heat 1cup of boiling water or 1 teapot of boiling water explain your . answer
Ramon Reply
I believe temperature being an intensive property does not change for any amount of boiling water whereas heat being an extensive property changes with amount/size of the system.
Someone
Scratch that
Someone
temperature for any amount of water to boil at ntp is 100⁰C (it is a state function and and intensive property) and it depends both will give same amount of heat because the surface available for heat transfer is greater in case of the kettle as well as the heat stored in it but if you talk.....
Someone
about the amount of heat stored in the system then in that case since the mass of water in the kettle is greater so more energy is required to raise the temperature b/c more molecules of water are present in the kettle
Someone
definitely of physics
Haryormhidey Reply
how many start and codon
Esrael Reply
what is field
Felix Reply
physics, biology and chemistry this is my Field
ALIYU
field is a region of space under the influence of some physical properties
Collete
what is ogarnic chemistry
WISDOM Reply
determine the slope giving that 3y+ 2x-14=0
WISDOM
Another formula for Acceleration
Belty Reply
a=v/t. a=f/m a
IHUMA
innocent
Adah
pratica A on solution of hydro chloric acid,B is a solution containing 0.5000 mole ofsodium chlorid per dm³,put A in the burret and titrate 20.00 or 25.00cm³ portion of B using melting orange as the indicator. record the deside of your burret tabulate the burret reading and calculate the average volume of acid used?
Nassze Reply
how do lnternal energy measures
Esrael
Two bodies attract each other electrically. Do they both have to be charged? Answer the same question if the bodies repel one another.
JALLAH Reply
No. According to Isac Newtons law. this two bodies maybe you and the wall beside you. Attracting depends on the mass och each body and distance between them.
Dlovan
Are you really asking if two bodies have to be charged to be influenced by Coulombs Law?
Robert
like charges repel while unlike charges atttact
Raymond
What is specific heat capacity
Destiny Reply
Specific heat capacity is a measure of the amount of energy required to raise the temperature of a substance by one degree Celsius (or Kelvin). It is measured in Joules per kilogram per degree Celsius (J/kg°C).
AI-Robot
specific heat capacity is the amount of energy needed to raise the temperature of a substance by one degree Celsius or kelvin
ROKEEB
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Source:  OpenStax, Precalculus. OpenStax CNX. Jan 19, 2016 Download for free at https://legacy.cnx.org/content/col11667/1.6
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