2017 #3 Free Response Question - AP Physics 1 - Exam Solution

The video tutorial covers question #3 from the 2017 AP Physics One exam, focusing on a rod and disk system. It explores maximizing angular speed through qualitative reasoning, equation analysis, and derivation. The tutorial also examines the plausibility of equations and compares collision outcomes, emphasizing the importance of understanding angular momentum and torque.

In the context of maximizing angular speed, where should the disk hit the rod?

• At Point C

• To the left of Point C

• To the right of Point C

• Anywhere along the rod

Why is it important to consider the distance X when maximizing angular speed?

• It affects the mass of the rod

• It alters the friction at the pivot

• It determines the initial angular momentum

• It changes the length of the rod

Does the equation found online agree with the reasoning in Part A?

• No, it contradicts the reasoning

• Yes, but only for small values of X

• Yes, it shows a larger X results in a larger angular speed

• No, it only applies to static systems

What is a key flaw in the student's incorrect equation in Part C?

• It implies mass is inversely proportional to angular speed

• It suggests mass is directly proportional to angular speed

• It assumes the rod is frictionless

• It neglects the length of the rod

Why is the mass of the disk important in determining angular momentum?

• It affects the rotational inertia of the rod

• It determines the initial velocity of the rod

• It contributes to the initial angular momentum

• It changes the pivot point

What is the correct expression for the post-collision angular speed derived in Part D?

• Mass of the disk times X divided by rotational inertia

• Initial velocity times X divided by mass of the disk

• Mass of the disk times initial velocity times X divided by rotational inertia plus mass times X squared

• Rotational inertia times X divided by mass of the disk

What is conserved during the collision in Part D?

• Angular momentum

• Potential energy

• Linear momentum

• Kinetic energy

How does the angular speed of the rod change if the disk bounces off instead of sticking?

• It becomes zero

• It remains the same

• It becomes greater than when the disk sticks

• It becomes less than when the disk sticks

What happens to the disk's velocity when it bounces off the rod?

• It remains unchanged

• It becomes positive

• It becomes zero

• It becomes negative

Why is it important to describe what happens to both the rod and the disk in Part E?

• To simplify the problem

• To ignore the disk's motion

• To focus only on the rod's behavior

• To ensure a complete understanding of the system