Angular Momentum Physics Overview

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Questions and Answers

Under what condition is linear momentum NOT conserved in a collision involving a fixed pivot?

Linear momentum is always conserved.
When the normal forces at the axle are internal forces.
When the normal forces at the axle are external forces. (correct)
When the collision is perfectly elastic.

When analyzing a collision where a blob sticks to a rotating object, what must be considered when calculating the final rotational inertia?

Only the rotational inertia of the original rotating object.
The final velocity of the blob and the initial angular velocity of the object.
The rotational inertia of the original object plus the rotational inertia of the blob about the new center of mass. (correct)
Only the mass of the blob.

In a 'free agent' collision, where no external torques are present, what quantity is conserved?

Only linear momentum.
Both linear and angular momentum. (correct)
Only angular momentum.
Only kinetic energy.

When a rotating dumbbell experiences friction, what effect does this have on its angular momentum and energy?

Both angular momentum and energy decrease. (C) Signup and view all the answers

How does the relationship between linear velocity (V) and rotational velocity (ω) change when an object is part of an extended rotating body, compared to a single particle?

V = ωR is only valid for extended bodies where all points are linked. (B) Signup and view all the answers

A disk and a ring have the same mass (M) and radius (R). Which has a larger moment of inertia?

The ring. (B) Signup and view all the answers

What does torque depend on?

The point which force is applied, force, and sine of the angle between them. (A) Signup and view all the answers

A uniform rod of length $L$ and mass $M$ is pivoted about one end. What is the moment of inertia about the pivot point?

$\frac{1}{3}ML^2$ (C) Signup and view all the answers

Which of the following equations correctly relates angular acceleration $(\alpha)$ to torque $(\tau)$ and moment of inertia $(I)$?

$\tau = I\alpha$ (A) Signup and view all the answers

What does the expression $\Sigma \vec{L} + \vec{\tau} \Delta t = \Sigma \vec{L}$ describe?

The conservation of angular momentum under the influence of torque. (A) Signup and view all the answers

If an object's angular velocity increases at a constant rate, which kinematic equation would be most appropriate to find the angular displacement ($\theta$) after a given time ($t$)?

$\theta = \theta_0 + \omega_0 t + \frac{1}{2} \alpha t^2$ (A) Signup and view all the answers

An object has a constant net force acting on it. What is true of the object?

It has constant linear momentum. (D) Signup and view all the answers

Under what circumstances will the work done be equal to $Fdcos(\theta)$?

Force is constant and displacement is along a straight line. (C) Signup and view all the answers

Which of the following statements about angular momentum is correct?

Angular momentum is a vector that points along the axis of rotation. (A) Signup and view all the answers

A particle moves in a circle of radius $r$ with a constant speed $v$. If the radius of the circle is doubled, how does the angular momentum of the particle change?

It is doubled. (D) Signup and view all the answers

A figure skater starts spinning with her arms extended. As she pulls her arms in, what happens to her angular velocity?

It increases. (B) Signup and view all the answers

What best describes the location of the center of mass?

All of the above. (D) Signup and view all the answers

Two objects have the same momentum, but different masses. Which object has more kinetic energy?

The object with the smaller mass. (B) Signup and view all the answers

When is kinetic energy conserved during a collision?

In a perfectly elastic collision. (C) Signup and view all the answers

What is the correct formula of the x-component of the center of mass?

$ X_{com} = \Sigma m_i x_i / \Sigma m_i $ (A) Signup and view all the answers

Flashcards

Linear Momentum

The measure of how hard it is to bring something to rest. It's a vector quantity; direction matters!

Angular Momentum (Extended Objects)

Measures how hard it is to completely stop the rotation of an object. It's a vector that points along the axis of rotation.