2018 #3 Free Response Question - AP Physics 1 - Exam Solution

The video tutorial covers question #3 from the 2018 AP Physics One exam, focusing on a spinning disk affected by frictional torque. It guides students through solving parts A to D, including graphing angular velocity and acceleration, deriving rotational inertia, and modeling torque with reduced friction. Emphasis is placed on careful graph drawing, as it accounts for a significant portion of the exam points.

What is the initial condition of the disk's angular velocity at time t = 0?

• Zero angular velocity

• Positive angular velocity

• Negative angular velocity

• Constant angular velocity

What is the effect of friction on the disk's angular acceleration?

• It causes a constant positive angular acceleration

• It causes a constant negative angular acceleration

• It causes a variable angular acceleration

• It has no effect on angular acceleration

How is the angular velocity graph described when friction is the only force acting?

• A horizontal line

• A line with a constant negative slope

• A curved line

• A line with a constant positive slope

What is the significance of the graphs in the context of the problem?

• They are less important than the equation derivation

• They are optional

• They are worth more points than the equation derivation

• They are not graded

What is the relationship between torque and rotational inertia in Part B?

• Torque equals rotational inertia times angular velocity

• Torque equals rotational inertia divided by angular acceleration

• Torque equals rotational inertia times angular acceleration

• Torque equals rotational inertia plus angular acceleration

What happens to the angular acceleration when oil is applied to the disk?

• It increases

• It remains constant

• It decreases

• It becomes zero

How does the angular velocity graph change after oil is applied?

• It curves upwards

• It remains unchanged

• It becomes a straight line

• It curves downwards

Which equation better models the torque when oil is present?

• Neither equation

• Both equations equally

• Equation 2

• Equation 1

Why is Equation 2 considered a better model for torque?

• It fluctuates randomly

• It remains constant

• It starts at a positive value and decreases

• It starts at zero and increases

What is the main focus of Part D in the problem?

• Deriving an equation for rotational inertia

• Calculating the initial angular velocity

• Sketching graphs for angular velocity

• Comparing mathematical models for torque