All AP Physics C: Mechanics Resources
Example Questions
Example Question #1 : Rotational Motion And Torque
What is the rotational equivalent of mass?
Moment of inertia
Radius
Torque
Angular momentum
Moment of inertia
The correct answer is moment of inertia. For linear equations, mass is what resists force and causes lower linear accelerations. Similarly, in rotational equations, moment of inertia resists torque and causes lower angular accelerations.
Example Question #1 : Understanding Linear Rotational Equivalents
In rotational kinematics equations, what quantity is analogous to force in linear kinematics equations?
Moment of inertia
Torque
Angular acceleration
Impulse
Torque
Just as force causes linear acceleration, torque causes angular acceleration. This can be seen most in the linear-rotational comparison of Newton's second law:
Example Question #1 : Rotational Motion And Torque
A boot is put in a stick which is attached to a rotor. The rotor turns with an angular velocity of
. What is the linear velocity of the boot?
Linear (tangential) velocity, is given by the following equation:
Here, is the angular velocity in radians per second and
is the radius in meters.
Solve.
Example Question #1 : Rotational Motion And Torque
A particle is moving at constant speed in a straight line past a fixed point in space, c. How does the angular momentum of the particle about the fixed point in space change as the particle moves from point a to point b?
The angular momentum decreases
The angular momentum increases
It cannot be determined without knowing the mass of the particle
The particle does not have angular momentum since it is not rotating
The angular momentum does not change
The angular momentum does not change
The angular momentum of a particle about a fixed axis is . As the particle draws nearer the fixed axis, both
and
change. However, the product
remains constant. If you imagine a triangle connecting the three points, the product
represents the
"of closest approach", labeled "
" in the diagram.
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All AP Physics C: Mechanics Resources
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