All AP Physics 1 Resources
Example Questions
Example Question #1 : Circular And Rotational Motion
A ferris wheel has a trip length of 3min, that is it takes three minutes for it to make one complete revolution. What is the angular velocity of the ferris wheel if it only takes passengers around one time, in ?
Angular velocity, in , is given by the length traveled divided by the time taken to travel the length:
We are told that the amount of time taken to make one revolution is 3min. One revolution is equal to , and 3 minutes is equal to 180 seconds. Divide the radian value by the seconds value to get the angular velocity.
Example Question #3 : Circular And Rotational Motion
A wheel makes one full revolution every seconds and has a radius of . Determine its angular velocity .
For this question, the angular velocity can be given by the equation:
, where is the angle made and is the time taken to make this angle.
In this problem, the wheel makes one full revolution() in seconds.
Therefore:
Example Question #1 : Angular Velocity And Acceleration
A CD rotates at a rate of in the positive counter clockwise direction. After pressing play, the disk is speeding up at a rate of . What is the angular velocity of the CD in after 4 seconds?
Given initial angular velocity, angular acceleration, and time we can easily solve for final angular velocity with:
Example Question #1001 : Ap Physics 1
If a ferris wheel has height of 100m, find the angular velocity in rotations per minute if the riders in the carts are going .
None of these
If the ferris wheel has height then it must have radius .
The circumference of the ferris wheel, or the distance of one rotation, is then:
Convert the given velocity into meters per minute, or :
Find rotations per minute:
Example Question #1 : Angular Velocity And Acceleration
A person of mass is riding a ferris wheel of radius . The wheel is spinning at a constant angular velocity of . Determine the linear velocity of the rider.
Convert to :
Example Question #11 : Circular And Rotational Motion
Radius of the earth:
A train is traveling directly north at . Estimate its angular velocity with respect to the center of the earth.
Convert to
Use the following relationship and plug in known values:
Example Question #12 : Circular And Rotational Motion
Pluto radius:
Determine the linear velocity of someone standing on the surface of Pluto due to the rotation of the planet.
Convert units of time into radians per second:
Convert to linear distance:
Example Question #1003 : Ap Physics 1
Pluto distance to sun:
Determine the translational velocity of Pluto.
Combine equations:
Convert to meters and seconds and plug in values:
Example Question #12 : Circular And Rotational Motion
Consider the following system:
Two spherical masses, A and B, are attached to the end of a rigid rod with length l. The rod is attached to a fixed point, p, which is at a height, h, above the ground. The rod spins around the fixed point in a vertical circle that is traced in grey. is the angle at which the L side of the rod makes with the horizontal at any given time ( in the figure and can be negative if mass A is above the horizontal).
As the rod rotates through the horizontal, the masses are traveling at a rate of . What is when mass A is at its highest point. Neglect air resistance and internal friction forces.
Note: is the angle between mass A and the horizontal and thus has a range of .
We can use the expression for conservation of energy to solve this problem:
Our initial state will be when the rod is horizontal, and our final state will be when mass A is at its highest point. If we assume that point p is at a height of 0 and the system is at rest and mass A is at its highest point, we can eliminate initial potential energy and final kinetic energy to get:
Expanding these terms and applying them to both masses, we get:
We don't need to separate the velocity components for each mass since they are always traveling at the same speed. Since the masses are attached to a rigid rod that spins around its midpoint, we know that the heights of the two masses (with respect to point p) will be equal and opposite. In expression form:
Substituting this into our equation, we get:
Rearranging for final height, we get:
We have values for all of these variables, so time to plug and chug:
Now we can use the sine function to determine what the angle c is at this point:
Where the opposite side is the height we just calculated and the hypotenuse is half the length of the rod. Therefore, we get:
Taking the inverse sine of both sides, we get:
Substituting in our values, we get:
Example Question #13 : Circular And Rotational Motion
A solid sphere of mass with a radius is held at rest at the top of a ramp with a length set at an angle above the horizontal. The sphere is released and allowed to role down the ramp. What is the instantaneous angular velocity of the sphere as it reaches the bottom of the ramp? Neglect air resistance and internal frictional forces.
Let's begin with the expression for conservation of energy:
The problem statement tells us that the sphere is initially at rest, so we can eliminate initial kinetic energy. Also, if we assume that the height at the bottom of the ramp is 0, we can eliminate final potential energy. We then have:
Then we can expand both of these terms. We need to remember that kinetic energy will have both a linear and rotational aspect. We then get equation (1):
Moving from left to right, let's begin substituting in expressions for unknown variables. The first term we don't know is height. However, we can use the length of the slope and the its angle to determine the height at the top of the ramp:
Rearranging for height, we get equation (2):
The next term we don't know is final velocity. We can use the relationship between angular and linear velocity:
Rearranging for linear velocity, we get equation (3):
Moving on, the next term we don't know is moment of inertia. We will use the expression for a sphere to get equation (4):
The last term is final rotational velocity. However, this is what we're solving for, so we'll leave it alone. Now let's substitute equations 2, 3, and 4 back into equation 1:
Multiplying each side the equation by , we get:
Factoring the right side of the equation:
Rearranging for final rotational velocity:
We know each of these values, so time to plug and chug:
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