Understanding AP Physics 1: Free Response Question 3

🔑The angular acceleration of a spinning disc is determined by the net torque acting on it. The net torque is the difference between the frictional torque and the applied torque.

🔑The graphs of angular velocity and acceleration for a spinning disc experiencing friction and torque can provide valuable information about the motion of the disc.

🔑Adding oil to the contact surface between the disc and the axle reduces friction and slows down the rate at which the disc's angular velocity decreases.

🔑The rotational inertia of a disc can be calculated using the equation: I = (τ₀ * t₁) / ω₀, where τ₀ is the frictional torque, t₁ is the time taken for the disc to come to rest, and ω₀ is the initial angular velocity.

🔑The change in the angular velocity of a spinning disc when the torque acting on it is constant can be represented by a straight line on the graph.

What factors influence the angular acceleration of a spinning disc?

—The angular acceleration of a spinning disc is influenced by the net torque acting on it, which is the difference between the frictional torque and the applied torque.

How does adding oil to the contact surface affect the motion of a spinning disc?

—Adding oil to the contact surface between the disc and the axle reduces friction, slowing down the rate at which the disc's angular velocity decreases.

What is the equation for calculating the rotational inertia of a disc?

—The rotational inertia of a disc can be calculated using the equation: I = (τ₀ * t₁) / ω₀, where τ₀ is the frictional torque, t₁ is the time taken for the disc to come to rest, and ω₀ is the initial angular velocity.

How can the motion of a spinning disc be represented graphically?

—The motion of a spinning disc can be represented graphically using graphs of angular velocity and acceleration. The angular velocity graph shows the change in angular velocity over time, while the angular acceleration graph shows the change in angular acceleration.

What is the relationship between the torque and the angular acceleration of a spinning disc?

—The torque acting on a spinning disc is directly proportional to its angular acceleration. A larger torque will result in a larger angular acceleration, while a smaller torque will result in a smaller angular acceleration.

00:02This video focuses on solving Free Response Question 3 from the 2018 AP Physics 1 exam.

01:19At time t=0, a disc starts spinning with an initial counterclockwise positive angular velocity.

02:39The angular acceleration of a spinning disc is determined by the net torque acting on it.

04:59The rotational inertia of a disc can be calculated using the equation: I = (τ₀ * t₁) / ω₀.

09:27Another approach to calculating the rotational inertia of a disc is using the equation: I = (τ₀ * t₁) / (ω₀ - 0).

11:13In another experiment, oil is added to the contact surface between the disc and the axle, reducing friction.

13:14The addition of oil slows down the rate at which the disc's angular velocity decreases.

13:32The graphs of angular velocity and acceleration for the disc change in the interval from one-half t₁ to t₁.