AP Calculus AB : Applications of Derivatives

Study concepts, example questions & explanations for AP Calculus AB

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Example Questions

Example Question #9 : Interpretation Of The Derivative As A Rate Of Change

A group of scientists use the following code for describing velocity and acceleration of particles:

, when both the velocity and acceleration are positive;
, when the velocity is positive, but the acceleration is negative;
, when the velocity is negative, but the acceleration is positive;
, when both the velocity and acceleration are negative.

What code - at t=2 - will the scientists use when describing a particle moving with a position function given by the following equation:

Possible Answers:

We need more information to determine the code used

Correct answer:

Explanation:

To determine which code the scientists will use, we must find the velocity and acceleration of the particle, given by the first and second derivatives of the position function, respectively, evaluated at the given point. 

The velocity and acceleration functions, therefore, are

The derivatives were found using the following rules:

Evaluated at t=2, we find that

When the velocity is positive, but the acceleration is negative, the code the scientists use is .

Example Question #31 : Applications Of Derivatives

Find the velocity of the particle at x=0, its position given by the following function:

Possible Answers:

Correct answer:

Explanation:

To determine the velocity of the particle, we must take the first derivative of the position function - in other words, the rate of change of the position is the velocity:

The derivative was found using the following rule:

To find the velocity at the given point, we simply plug in the value into the velocity function:

Example Question #11 : Interpretation Of The Derivative As A Rate Of Change

The velocity of a particle in feet per second can be modeled by the function

What is the acceleration of this particle at 6 seconds?

Possible Answers:

Correct answer:

Explanation:

The acceleration of a particle is its change in velocity; therefore, to find its acceleration at a particular point in time, it is necessary to take the derivative of the velocity function and evaluate it for that value.  In short, we want 

Differentiate :

Apply the sum rule:

Apply the chain rule by setting :

This is the acceleration function; substitute 6 for :

Example Question #12 : Interpretation Of The Derivative As A Rate Of Change

The velocity of a particle in feet after  seconds can be modeled by the equation 

.

At  seconds, give the acceleration of this particle in feet per second squared.

Possible Answers:

Correct answer:

Explanation:

The acceleration function of a particle with respect to time is the derivative  of the velocity function of the particle. 

Find this derivative by first using the product rule:

Apply the product rule:

Evaluate :

 feet per second squared.

Example Question #13 : Interpretation Of The Derivative As A Rate Of Change

Determine the velocity of a particle at x=10 when the position function is given by

Possible Answers:

Correct answer:

Explanation:

To determine the velocity function - the rate of change of position - we must take the derivative of the position function:

The derivative was found using the following rules:

To find the velocity at a certain value of x - the instantaneous rate of change of position - we simply plug in the given value of x into the velocity function:

 

Example Question #14 : Interpretation Of The Derivative As A Rate Of Change

A crystal forms at a rate given by the following equation:

What is the rate of change of the crystal growth rate at t=5?

Possible Answers:

None of the other answers

Correct answer:

Explanation:

To find the rate of change of crystal growth at a given time, we must take the derivative of the growth rate function and evaluate it at a specific time.

The derivative of the function is

and was found using the following rules:

Now, to find the growth rate at t=5, simply plug in this value for t into the derivative function:

Example Question #15 : Interpretation Of The Derivative As A Rate Of Change

If p(t) gives the position of a planet as a function of time, find the function which models the planet's acceleration.

 

Possible Answers:

Correct answer:

Explanation:

If p(t) gives the position of a planet as a function of time, find the function which models the planet's acceleration.

Velocity is the first derivative of position. Acceleration is the first derivative of velocity.

Therefore, all we need to do to solve this problem is to find the second derivative of p(t).

We can do this via the power rule and the rule for differentiating sine and cosine.

1) 

2) 

So, we these rules in mind, we get:

So our velocity function is:

Next, differentiate v(t) to get a(t).

So, our acceleration function is

Example Question #31 : Applications Of Derivatives

If p(t) gives the position of a planet as a function of time, find the planet's acceleration when t=0.

Possible Answers:

Correct answer:

Explanation:

If p(t) gives the position of a planet as a function of time, find the planet's acceleration when t=0.

Velocity is the first derivative of position. Acceleration is the first derivative of velocity.

Therefore, all we need to do to solve this problem is to find the second derivative of p(t) and then plug in 0 for t and solve.

We can do this via the power rule and the rule for differentiating sine and cosine.

1) 

2) 

So, we these rules in mind, we get:

So our velocity function is:

Next, differentiate v(t) to get a(t).

So, our acceleration function is

Next, plug in 0 and simplify.

Our answer is 12. Since we are not given any units, we can leave it as 12

Example Question #17 : Interpretation Of The Derivative As A Rate Of Change

A car is moving with a velocity that can be modeled by the equation

What is the cars acceleration at 

Possible Answers:

Correct answer:

Explanation:

The car's acceleration is the instantaneous rate of change in its velocity with respect to time (), so we can find the value of the cars acceleration at any time by taking the derivative of the velocity equation

Evaluating at , we get

Example Question #18 : Interpretation Of The Derivative As A Rate Of Change

A body's position "s" is given by the equation:

    ,   

 

a) Find the body's speed at the endpoints of the given interval

b) Find the body's acceleration at the endpoints of the given interval

Possible Answers:

Correct answer:

Explanation:

We are given the function describing the position of the body given a time "t":

We are also given the interval that the function can be applied over: 

First, we are tasked to find the speed of the body at each of the endpoints (0 and 2 seconds, respectively). 

To figure this, we must understand that speed is the absolute value of velocity

To find the velocity function, we must take the derivative of the position function with respect to time:

                                  

                                  

Now that we have the function of velocity given a time "t", we can find the speed of the body given a time "t" by simply taking the absolute value of the velocity function. 

Now, to find the speed of the endpoints:

 

We can repeat the same process to find the speed at 2 seconds.

 

For part a, the speeds at 0 and 2 seconds are 3 and 1 [m/s], respectively. 

Part b asks us to find the acceleration at the endpoint times (0 and 2 seconds). To do this, we must first understand that to find acceleration at a time "t", we must take the derivative, with respect to time, of the velocity function

From part a, we found the velocity function:

Thus, to find acceleration, we derive this function with respect to time.

                                 

                                  

                                  

The result of our derivation tells us that no matter what time is plugged into the function, the acceleration shall always return 2[m/s^2].

So, for part b, the acceleration at 0 and 2 seconds are 2 and 2 [m/s^2], respectively. 

 

 

 

 

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