AP Physics 1 : AP Physics 1

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #571 : Ap Physics 1

Consider the following system:

Frictionless pully

Two masses, A and B, are attached to the end of a rope that runs through a frictionless pulley.

The system is initially rest. At time , the system begins to move. After mass A has traveled , what is its velocity?

Possible Answers:

Correct answer:

Explanation:

First, we need to determine the rate at which the masses accelerate. We will start with Newton's 2nd law:

There are two forces acting on the system: gravity on each mass. For simplicity sake, we will examine these forces with respect to mass. Therefore, the force on mass B becomes an upward tension force on mass A. Now we need to clarify which direction is positive. For this problem, we'll say that a downward force is positive, and an upward force is negative.

We'll start with the gravitational force:

Now for tension. The tension force is simply the gravitational force applied to mass B:

Note that it's negative because it is in the upward direction

Now adding these together to get the net force:

Substituting this back into the original equation, we get:

Where m is the combination of both masses:

Rearrange for acceleration:

Now we can use a kinematics equation:

We are told that the system is initially at rest, so we can eliminate that term:

Rearranging for time, we get:

We know these values, so we can solve for time:

Now we can solve for final velocity using:

Example Question #571 : Ap Physics 1

An an archer has shot an arrow at an angle of  above the horizontal with an initial velocity of . How far has the arrow traveled horizontally by the time it reaches its highest point? Neglect air resistance.

Possible Answers:

Correct answer:

Explanation:

The arrow will have a vertical velocity of 0 when it reaches it's high point. Therefore, we can use the initial vertical velocity to calculate how long it takes to get there:

Then using the follow expression to determine time:

We can then multiply this time by the horizontal component of the arrow's velocity, which is constant since we are neglecting air resistance:

Plug this value into the distance formula to find the range.

Example Question #21 : Fundamentals Of Displacement, Velocity, And Acceleration

An archer is riding a horse that is galloping at a rate of  to the north. If the archer shoots an arrow directly east at an angle of above the horizontal and with a velocity of , what is the velocity of the arrow relative to the ground?

Possible Answers:

Correct answer:

Explanation:

To calculate the arrow's velocity relative to the ground, we will need to combine the velocity of the archer and the velocity of the arrow relative to the archer. To do this, we will first need to split the velocity of the arrow relative to the archer into it's vertical and horizontal components:

Then we can combine the two horizontal velocities (archer and arrow relative to archer). However, it should be noted that these two velocities are at right angles to each other (north and east), so we will need to use Pythagorean's theorem to combine them:

Now we can combine our total horizontal velocity with the vertical velocity to get our total velocity:

Example Question #571 : Ap Physics 1

Two cars are racing side by side on a perfectly circular race track. The inner car is from the center of the track. The outer car is from center of the track.

If the outer car accelerates from to , determine the angular acceleration.

Possible Answers:

None of these

Correct answer:

Explanation:

Example Question #571 : Ap Physics 1

A police officer sees a car in a  zone approaching a stop sign.  The driver doesn't see the sign until the last minute and then slams on his breaks, decelerating at a constant rate to a stop just before the sign, but leaves a skid mark  long.  Reviewing the dash-cam tape, the officer is able to tell that the car took  to stop.  Was the driver speeding?  Assume the wheels locked when the brakes were applied.

Possible Answers:

Yes, the car was traveling approximately 

No, the car was traveling approximately 

No, the car was traveling approximately 

Yes, the car was traveling approximately

No, the car was traveling approximately 

Correct answer:

Yes, the car was traveling approximately 

Explanation:

To find how fast the driver was going before applying the brakes, we use the following kinematics formula since acceleration is constant:

Where  is the displacement,  is the initial velocity (before applying the brakes),  is the final velocity (which is zero since the car came to a stop), and  is time. We can now plug in the known values into the above equation and solve for the initial velocity:

In order to know if the driver was speeding, we must convert this speed and/or the speed limit in the same units. Let's put this speed in kilometers per hour.

As we can see, the driver was exceeding the  speed limit and was thus speeding.

Example Question #292 : Linear Motion And Momentum

A submarine launches a missile from underwater. The missile passes through the surface of the sea at a velocity of . At this point, a thruster ignites, causing the missile to accelerate in a straight line at . After 10 seconds of acceleration, how far has the missile traveled?

Possible Answers:

Correct answer:

Explanation:

We need our kinematic equation that relates displacement, initial velocity, and acceleration:

We can neglect gravity in this problem since the statement says that the missile accelerates in a straight line at a constant rate.

Plugging in our values, we get:

Example Question #571 : 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 #573 : Ap Physics 1

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 #573 : 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 #574 : 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).  

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