AP Physics 1 : Fundamentals of Displacement, Velocity, and Acceleration

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #577 : Ap Physics 1

 is the minimum speed needed for an airplane to take off.  The airplane is accelerating at a constant .  What length does the runway need to be?  

Possible Answers:

Correct answer:

Explanation:

The correct answer is .  Because we don't have time, we should use an equation that does not require a time variable, like 

where  is the final velocity,  is the initial velocity,  is the acceleration, and  is the distance traveled.  We are given , , and .  Therefore, we can put these values into our equation to solve for :

Example Question #31 : Fundamentals Of Displacement, Velocity, And Acceleration

A car is moving with a velocity given by  after being ejected by a connon at an initial velocity of .

When is the acceleration equal to ?

Possible Answers:

Correct answer:

Explanation:

In order to find the acceleration, you must first take the derivative of the velocity:

The initial velocity does not affect the acceleration! It would only affect the position function! Afterwards, just plug in and solve for t:

Example Question #579 : Ap Physics 1

You drive  east from your home past the grocery store. As you pass the store, you drive another  eastward to the post office. From the post office, you drive  westward.  Then, you drive  east back home. Assume you do not stop and are traveling at a constant speed. The trop takes you  total. What was your average speed? Your average velocity? (average speed, average velocity)

Possible Answers:

,

,

,

 ,

Correct answer:

 ,

Explanation:

The correct answer is , .  Average speed is:

, in 

We traveled a total of . Convert this to meters to get 

Then we must convert  to

Then divide to get your average speed. This gives us  

Velocity, on the other hand, is   in .  

Displacement is the the final distance from the initial position. Displacement is considered a state function. Only the final position matters; it doesn't matter how you get there. For example, if you start at point A and drive in a circle that covers , and end up at point A again, your displacement is . This is because your final position is the same as your initial position. So in this problem, because your final position is the same as your initial position, your displacement is .  

So for the average velocity.  

Example Question #580 : Ap Physics 1

On your way home from school, you drive  until you pass John's house. Once you pass John's house you drive another  in the same direction until you reach the park, where you have soccer practice. The trip takes you . What is your average speed? Your average velocity? (Average speed, average velocity).

Possible Answers:

,

,  

,

,  

Correct answer:

,

Explanation:

The correct answer is 

Remember average speed is , also  

By converting  to  and  to , we get

This is also true for average velocity. Average velocity is  ,    

Displacement is the distance of the final position from the initial position. Because we do not change direction, the displacement is equal to the distance. That means that the average velocity will be equal to the average speed (time remains constant).  

Example Question #31 : Fundamentals Of Displacement, Velocity, And Acceleration

A car drives  in  at constant velocity and without changing direction. What is the car's acceleration?  

Possible Answers:

Correct answer:

Explanation:

Average acceleration is equal to , where  is the final velocity and  is the initial velocity.  

If the velocity is constant, the final and initial velocities are equal. Let's say the car is traveling at  constantly.

 .  So  

When velocity is constant, acceleration is always equal to

Example Question #541 : Newtonian Mechanics

 A car accelerates to  from rest in . Assume the car moves in a straight line. What is the magnitude of the car's acceleration? 

Possible Answers:

Correct answer:

Explanation:

Average acceleration is equal to  where  is the final velocity and  is the initial velocity.  

In this problem, we know our initial velocity is  (starting from rest). The final velocity is . We must convert these units to .  

Using these values, we can calculate the final velocity to be

Using this number, we can finally calculate the magnitude of acceleration.  

Example Question #33 : Fundamentals Of Displacement, Velocity, And Acceleration

A car at a stop sign must cross an intersection that is  long. If the car accelerates at  constantly, how long will it take for the car to cross the intersection?

Possible Answers:

Correct answer:

Explanation:

We can solve this problem using the kinematic equation:

Where  is the displacement,  is the initial velocity,  is the acceleration, and  is time.  We are given values for all but the time. Therefore, we may plug these values into the above equation and solve for .

Example Question #31 : Fundamentals Of Displacement, Velocity, And Acceleration

A ball is thrown upward at  from a tower. Ignore air resistance. How far does the ball travel after ?

Possible Answers:

Correct answer:

Explanation:

The correct answer is . We can use the kinematics equation:

We are given the values of , , and  (initial velocity, time, and acceleration). Therefore we can solve for  to find the distance traveled by the ball.  

 is negative because the position of the ball is  below its initial point.  

Example Question #35 : Fundamentals Of Displacement, Velocity, And Acceleration

From the top of a mountain, you throw a rock downward at . What is the rock's displacement after ?

Possible Answers:

Correct answer:

Explanation:

To solve this problem, we can use the kinematics equation:

Where is the initial velocity,  is time, and  is acceleration. We are given all of these variables, so we can plug them in for .  

In this problem,  and  are negative because the rock is initially being thrown downhill and is accelerating downwards.

Example Question #32 : Fundamentals Of Displacement, Velocity, And Acceleration

If the driver of a  car traveling at slams on the brakes, and it takes  for the car to come to a complete stop, what is the coefficient of kinetic friction between the car's tires and the asphalt that the car is traveling on?

Possible Answers:

Correct answer:

Explanation:

The first step in doing this problem is figuring out how many forces are acting on the car when the driver slams the brakes. Since there is nothing pushing the car in the direction that it was originally traveling, the only force that is acting on the car is the force of friction. This means that the net force is simply just the force of kinetic friction, net force is also equal to mass multiplied by acceleration, so this equation appears as follows:

where  is the force of kinetic friction. 

The force of friction is also equal to normal force multiplied by the coefficient of kinetic friction for a certain surface. This equation appears as follows:

where  is the force of kinetic friction,  is the coefficient of kinetic friction, and N is normal force (also equal to mass x gravity).

These 2 equations can be connected in order to figure out the coefficient of kinetic friction.

mass can be cancelled from both sides. Acceleration is found as follows:

By plugging in the given values,  is found to be:

 

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