AP Physics 1 : Circular, Rotational, and Harmonic Motion

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #9 : Period And Frequency

A car with wheels of mass and wheels of radius is traveling at . Treating the wheels as disks of uniform mass density, calculate the angular frequency of one wheel.

Possible Answers:

None of these

Correct answer:

Explanation:

Example Question #10 : Period And Frequency

A car with wheels of mass and wheels of radius is traveling at . Treating the wheels as disks of uniform mass density, calculate the angular period of one wheel.

Possible Answers:

None of these

Correct answer:

Explanation:

First, find the angular frequency:

Angular period is the inverse of angular frequency:

Example Question #121 : Circular And Rotational Motion

A bowling ball of mass  and radius  is thrown with a rotational kinetic energy of . Find its period.

Possible Answers:

Correct answer:

Explanation:

The expression for rotational kinetic energy is:

Where I is the moment of inertia for a solid sphere:

And w is the angular velocity:

Plugging these in, we get:

Rearranging for linear velocity:

The expression for period is the circumference of the ball divided by the linear velocity of the ball:

Plugging in expressions, we get:

We have all of these values, so time to plug and chug:

Example Question #1081 : Newtonian Mechanics

A ferris wheel has a diameter of 60 meters. The carriages on the outside of the wheel are traveling at an instantaneous velocity of . What is the period of rotation of the wheel?

Possible Answers:

Correct answer:

Explanation:

We can calculate the circumference of the wheel using the given radius:

We can use this and the given velocity to find the period:

Example Question #1 : Period And Frequency Of Harmonic Motion

A horizontal spring on a frictionless surface has a spring constant of  with a mass of  attached to the end of the spring. If the spring is stretched  passed its point of equilibrium and released, how many times does the mass pass through equilibrium per minute?

Possible Answers:

Correct answer:

Explanation:

We need to know three things to solve this problem.

  1. Formula for frequency of a spring in simple harmonic motion
  2. The spring constant
  3. Mass of object attached to spring

We're given 2 and 3, so we just need to know 1.

The formula for frequency is:

Plugging in our values, we get:

Now we need to convert Hertz (cycles per second) to cycles per minute.

To get to these units:

Example Question #2 : Period And Frequency Of Harmonic Motion

Consider the following system:

Pendulum_1

If the period of the pendulum is , what is the length of the string?

Possible Answers:

Correct answer:

Explanation:

We simply need the expression for the period of a pendulum to solve this problem:

Rearranging for length, we get:

We have all of these values, allowing us to solve:

Example Question #3 : Period And Frequency Of Harmonic Motion

Consider the following system:

Pendulum_1

If the mass reaches a maximum height of  and the minimum angle is , what is the period of the pendulum?

Possible Answers:

Correct answer:

Explanation:

First, we will be using the equation for the period of a pendulum:

The only value we don't have is length. However, we can develop an expression for length from the given information.

The second term describes how close the pendulum gets to the height of the top of the pendulum. Therefore, we subtract this value from the lowest point of the pendulum to get the height relative to its lowest point. We can rewrite this as:

Substituting this into the original expression for the period, we get:

We can use our given values to solve:

Example Question #4 : Period And Frequency Of Harmonic Motion

A block of mass 1.3 kg is attached to a spring whose force constant, , is .  What is the frequency and period of the oscillations of this spring-block system?

Possible Answers:

Correct answer:

Explanation:

For a mass-spring system undergoing simple harmonic motion, the frequency of the oscillations can be found using the equation

We were given the force constant (or spring constant), , to be . The oscillating mass was also given to be 1.3 kg. So, plug these in to the equation and solve for frequency, . The unit for frequency is Hertz, Hz.

Example Question #5 : Period And Frequency Of Harmonic Motion

A 300 g mass is attached to a spring and undergoes simple harmonic motion with a period of 0.25 s.  If the total energy of the system is 3.0 J, what is the aplitude of the oscillations?

Possible Answers:

Correct answer:

Explanation:

We were given the mass of the system as 300 g. First, we should convert this to kilograms. Since , we can convert by

They also told us the period of the oscillations, which is 0.25 s.  We can use the following equation to solve for the force constant:

Rearrange the equation to isolate the variable , and substitute in the known values to solve for :

Now that we have the force constant, , we can use this to help us find the amplitude of the oscillations. We were also given the energy of the system to be 3.0 J. The equation for the energy of a mass-spring oscillating system is:

 

 is the total potential energy of the system. Now, plug in values and solve for , which is the amplitude of the oscillations.

Example Question #6 : Period And Frequency Of Harmonic Motion

A pendulum of length  undergoing simple harmonic motion has a period of 1.0 s on Earth. If the acceleration of gravity on the Moon is , what would the period of the pendulum be on the Moon?

Possible Answers:

Correct answer:

Explanation:

The equation that relates the period of a pendulum and its length is

We know the period of the pendulum on Earth, which was given, to be 1.0 s. We also know that  on Earth is .  So, we can find the length of the pendulum:

Now that we have the length of the pendulum, we can use this to calculate what the period of oscillation will be if the pendulum was on the Moon where the "g" is not the same as on Earth, but rather is .

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