Free Practice Quiz Question List

6 Angular Momentum Online Quiz Questions

Use this free practice quiz with 20 questions to review 6 Angular Momentum, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

True or false: A particle's angular momentum can depend on the point about which it is measured.

A
True
B
False

Choose one

1 point

Which is the SI unit of angular momentum?

A
$\mathrm{kg\,m/s}$
B
$\mathrm{kg\,m^2/s}$
C
$\mathrm{N\,m/s}$
D
$\mathrm{kg/s^2}$

Fill in the blank

1 point

The direction of $\mathbf L=\mathbf r\times\mathbf p$ , perpendicular to the plane of $\mathbf r$ and $\mathbf p$ , is given by the .

True or false

1 point

True or false: A force directed toward or away from a fixed center produces zero torque about that center.

A
True
B
False

Choose one

1 point

A force $\mathbf F$ acts at position $\mathbf r$ relative to an origin. Which expression gives its torque about that origin?

A
$\boldsymbol\tau=\mathbf F\times\mathbf r$
B
$\boldsymbol\tau=\mathbf r\cdot\mathbf F$
C
$\boldsymbol\tau=\mathbf r\times\mathbf F$
D
$\boldsymbol\tau=\mathbf r+\mathbf F$

Fill in the blank

1 point

For a system, total angular momentum remains constant when the net external torque is .

Choose one

1 point

A skater spins at $2.0\,\mathrm{rad/s}$ with moment of inertia $4.0\,\mathrm{kg\,m^2}$ . With negligible external torque, the skater reduces the moment of inertia to $2.0\,\mathrm{kg\,m^2}$ . What is the final angular speed?

A
$4.0\,\mathrm{rad/s}$
B
$2.0\,\mathrm{rad/s}$
C
$1.0\,\mathrm{rad/s}$
D
$8.0\,\mathrm{rad/s}$

Written response

1 point

What is the motion called when an external torque causes a gyroscope's spin axis to change direction?

Written response

1 point

A rigid body rotates about a fixed axis with moment of inertia $3\,\mathrm{kg\,m^2}$ and angular velocity $2\,\mathrm{rad/s}$ . What is its angular momentum value in kg m^2/s?

Choose all

1 point

Select all statements consistent with the angular-momentum principles described here.

A
If the net external torque is zero, total angular momentum remains constant.
B
Angular momentum is conserved only when rotational kinetic energy is constant.
C
A change in angular momentum requires a nonzero net torque over the relevant interval.
D
A skater can gain rotational kinetic energy while conserving angular momentum if muscles do work.

Open ended

1 point

Describe the steps for deciding whether angular momentum conservation can be applied to a rotating system, and state the relation used for fixed-axis rotation when it can.

Choose all

1 point

Select all statements that correctly describe the angular momentum of a system of particles.

A
The system's total angular momentum is the vector sum of its particles' angular momenta.
B
The rate of change of a system's total angular momentum equals the net external torque.
C
Internal torques always change the total angular momentum of an isolated system.
D
Under the usual Newtonian assumptions, internal torques cancel for an isolated system.

True or false

1 point

True or false: In general three-dimensional rotation, angular momentum must point in the same direction as angular velocity.

A
True
B
False

Choose one

1 point

A particle moves under a central force toward a fixed center. Its distance and speed vary, but the force always points along the line to the center. What can be concluded about its angular momentum about that center?

A
Its angular momentum changes whenever its distance from the center changes.
B
Its angular momentum remains constant because the torque about the center is zero.
C
Its angular momentum remains constant only if its speed is constant.
D
Its angular momentum is zero because the force points toward the center.

Choose one

1 point

A particle is at position $\mathbf r$ relative to an origin, and a force $\mathbf F$ parallel to $\mathbf r$ acts on it. What is the torque about that origin?

A
The torque is zero.
B
The torque is nonzero and parallel to $\mathbf r$ .
C
The torque is nonzero and parallel to $\mathbf F$ .
D
The torque has the same magnitude as the force.

Choose one

1 point

A particle moves under a force directed toward or away from a fixed center. Which conclusion follows about its angular momentum about that center?

A
The particle's angular momentum must increase as its distance decreases.
B
The particle's angular momentum is conserved only if its speed is constant.
C
The particle's angular momentum about the center is conserved, even if its distance and speed vary.
D
The particle's angular momentum is conserved only if the force is zero.

Choose one

1 point

A particle's position vector points in the positive $x$ -direction and its momentum points in the positive $y$ -direction. In which direction does its angular momentum point?

A
The negative $z$ -direction.
B
The positive $z$ -direction.
C
The positive $x$ -direction.
D
The positive $y$ -direction.

Written response

1 point

An external torque causes a spinning object's spin axis to change direction. What is this motion called?

Choose one

1 point

A body rotates about a fixed axis at $6\,\mathrm{rad/s}$ . Its moment of inertia triples while the net external torque is zero. What is its final angular speed?

A
$0\,\mathrm{rad/s}$
B
$6\,\mathrm{rad/s}$
C
$2\,\mathrm{rad/s}$
D
$18\,\mathrm{rad/s}$

Written response

1 point

A body rotating about a fixed axis has initial moment of inertia $0.80\,\mathrm{kg\,m^2}$ and angular speed $5.0\,\mathrm{rad/s}$ . Its moment of inertia changes to $0.50\,\mathrm{kg\,m^2}$ , with negligible external torque. What is its final angular speed? Enter the value in rad/s.