AP Calculus AB : Derivative interpreted as an instantaneous rate of change

Study concepts, example questions & explanations for AP Calculus AB

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1271 : Ap Calculus Ab

A particles position at any point in time can be modeled by the following equation

Find the velocity of the particle when 

Possible Answers:

Correct answer:

Explanation:

The velocity is the instantaneous rate of change of the particles position with respect to time (), so by taking the derivative of the function we can find the particles velocity ant any point in time

Evaluating at the time we specified in the problem statement, we get

Example Question #712 : Derivatives

The amount of bacteria in a dish (as a function of time) is modeled according to the following expression:

At what time will the amount of bacteria be growing at a rate of 38?

Possible Answers:

None of the other answers

Correct answer:

Explanation:

To determine the rate of change of the amount of bacteria at a specific time, we must take the derivative of the function:

The derivative was found using the following rules:

Now, we are asked to find the time corresponding to a certain rate of growth of the bacteria. This is the output of the derivative function, from a certain time input into the function. So, we must solve for the time that gets us 38 as our output:

 

Example Question #1271 : Ap Calculus Ab

An electron in motion can be described by the following equation, which gives its position at any point in time

Find the speed of the electron when 

Possible Answers:

Correct answer:

Explanation:

To find the velocity of the electron, we take the derivative of its position equation. Velocity is the instantaneous rate of change ofposition with respect to time, which we will evaluate at a specified time

Evaluating when 

Example Question #31 : Derivative Interpreted As An Instantaneous Rate Of Change

A car going up a hill can be described by the following equation:

How fast is the car moving at the time 

Possible Answers:

Correct answer:

Explanation:

The cars velocity is the instantaneous rate of change of the position with respect to time, , so by taking the derivative of the function we can get the velocity equation which can be evaluated for any time 

Evaluated at , we get

 

Example Question #31 : Derivative Interpreted As An Instantaneous Rate Of Change

Given that h(t) represents the height of a frisbee as a function of time, find the  frisbee's velocity when .

Possible Answers:

Correct answer:

Explanation:

Given that h(t) represents the height of a frisbee as a function of time, find the  frisbee's velocity when .

To find the velocity function from a height or position function, we simply need to find the first derivative of the function. Then, to find the velocity at a given value of t, simply plug the value of t into the velocity function.

Recall the power rule:

This states that we can find the derivative of any polynomial by taking each term, multiplying by its exponent, and then subtracting one from the exponent.

Doing so yields:

Notice that our 14 dropped out. Any constant terms will drop our while differentiating.

Change it to v(t) and we are almost there.

We need v(1.5)

So, we get -264.75. This might seem like a strange velocity for a frisbee, but we don't know the units, so it might make sense within the relevant system.

Example Question #32 : Derivative Interpreted As An Instantaneous Rate Of Change

Given that h(t) represents the height of a frisbee as a function of time, find the  frisbee's acceleration when .

Possible Answers:

Correct answer:

Explanation:

Given that h(t) represents the height of a frisbee as a function of time, find the  frisbee's acceleration when .

To find the acceleration function, we need to recall that velocity is the first derivative of position, and that acceleration is the first derivative of velocity. In other words, we need to find our second derivative. Once we have that, we need to plug in -1 for t.

Recall the power rule:

This states that we can find the derivative of any polynomial by taking each term, multiplying by its exponent, and then subtracting one from the exponent.

Doing so yields:

Notice that our 14 dropped out. Any constant terms will drop our while differentiating.

Change it to v(t) and we are almost there.

Next, find the derivative of v(t), again with the power rule.

Making our acceleration function:

Now, finally, plug in -1 for t and solve.

So, our acceleration is:

-754

We have no units, so although this number may seem a little strange, we can;t really say much about it.

Learning Tools by Varsity Tutors