AP Calculus BC : Derivatives

Study concepts, example questions & explanations for AP Calculus BC

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Example Questions

Example Question #181 : Derivatives

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A particle moves around the xy plane such that its position as a function of time is given by the parametric function:

 .

What is the slope, , of the particle's trajectory when ?

Possible Answers:

Correct answer:

Explanation:

Evaluate the slope as

 .

We have

and

so

Evaluating this when  gives

.

Remark: This curve is one example from family of curves called Lissajous figures, which can be observed on oscilloscopes.

Example Question #1 : First And Second Derivatives Of Functions

The position of a car is given by the following function:

What is the velocity function of the car?

Possible Answers:

Correct answer:

Explanation:

The velocity function of the car is equal to the first derivative of the position function of the car, and is equal to

The derivative was found using the following rules:

,  

Example Question #1 : Velocity, Speed, Acceleration

Let 

Find the first and second derivative of the function.

Possible Answers:

Correct answer:

Explanation:

In order to solve for the first and second derivative, we must use the chain rule.

The chain rule states that if

 

and 

then the derivative is

In order to find the first derviative of the function

we set

and

Because the derivative of the exponential function is the exponential function itself, we get

And differentiating  we use the power rule which states

As such

And so

 

To solve for the second derivative we set 

and 

Because the derivative of the exponential function is the exponential function itself, we get

And differentiating  we use the power rule which states

As such

And so the second derivative becomes

 

Example Question #2 : Velocity, Speed, Acceleration

Find the velocity function of the particle if its position is given by the following function:

Possible Answers:

Correct answer:

Explanation:

The velocity function is given by the first derivative of the position function:

and was found using the following rules:

Example Question #3 : Velocity, Speed, Acceleration

Find the first and second derivatives of the function

Possible Answers:

Correct answer:

Explanation:

We must find the first and second derivatives.

We use the properties that

  • The derivative of    is  
  • The derivative of   is  

As such

To find the second derivative we differentiate again and use the product rule which states

Setting

  and  

we find that

As such

Example Question #3 : Velocity, Speed, Acceleration

Given the velocity function

where  is real number such that , find the acceleration function

.

Possible Answers:

Correct answer:

Explanation:

We can find the acceleration function  from the velocity function by taking the derivative:

We can view the function

as the composition of the following functions

 

so that . This means we use the chain rule

to find the derivative. We have  and , so we have

Example Question #1 : Velocity, Speed, Acceleration

The position of an object is given by the equation . What is its acceleration at t = 2? 

Possible Answers:

Correct answer:

Explanation:

If this function gives the position, the first derivative will give its speed and the second derivative will give its acceleration. 

Now plug in 2 for t: 

Example Question #6 : Velocity, Speed, Acceleration

The equation  models the position of an object after t seconds. What is the acceleration at 3 seconds? 

Possible Answers:

Correct answer:

Explanation:

If this function gives the position, the first derivative will give its speed and the second derivative will give its acceleration. 

Plug in 3 for t: 

Example Question #1 : Velocity, Speed, Acceleration

The equation  models the position of an object after t seconds. What is its speed after  seconds? 

Possible Answers:

Correct answer:

Explanation:

If this function gives the position, the first derivative will give its speed.

Plug in  for t: 

Example Question #2 : Velocity, Speed, Acceleration

The position of an object is modeled by the equation What is the speed after  seconds? 

Possible Answers:

Correct answer:

Explanation:

If this function gives the position, the first derivative will give its speed. To differentiate, use the chain rule: . In this case,  and . Since  and , the first derivative is 

Plug in  for t: 

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