All Flashcards
What is the effect of applying an external torque to a rotating object?
The object's angular momentum changes. The change is equal to the angular impulse imparted by the torque.
What happens if a spinning object's mass distribution changes, moving mass closer to the axis of rotation?
The moment of inertia decreases, and the angular speed increases to conserve angular momentum.
What is the effect of zero net external torque on a system?
The total angular momentum of the system remains constant.
What happens when a rotating object collides with a stationary object and they stick together?
The final angular velocity of the combined system will be lower than the initial angular velocity of the rotating object, due to the increased moment of inertia. Total angular momentum is conserved.
What is the effect of a figure skater pulling their arms inward during a spin?
Their moment of inertia decreases, causing their angular speed to increase, conserving angular momentum.
What happens when a spacecraft fires thrusters?
It creates an angular impulse, changing its rotational motion.
Define conservation of angular momentum.
The total angular momentum of a closed system remains constant unless acted upon by an external torque.
What is angular impulse?
Angular impulse is the product of the net torque and the time interval over which it acts. Units are .
Define moment of inertia.
A measure of an object's resistance to changes in its rotation rate. It depends on the mass distribution of the object and the axis of rotation.
What is a closed system in the context of angular momentum?
A system where no external torques act upon it, allowing angular momentum to be conserved.
Define angular momentum.
The rotational equivalent of linear momentum. For a point particle, it is given by , where is the position vector and is the linear momentum.
What is the key difference between angular momentum and linear momentum?
Angular momentum is for rotational motion, while linear momentum is for straight-line motion. Both are conserved, but under different conditions.
Compare the effects of internal vs. external forces on angular momentum.
Internal forces do not change the total angular momentum of a system. External forces (torques) are required to change the total angular momentum.
Compare a system with zero external torque and a system with nonzero external torque in terms of angular momentum.
Zero external torque: Angular momentum is conserved and remains constant. Nonzero external torque: Angular momentum changes due to angular impulse from the torque.
Compare the roles of moment of inertia and angular velocity in determining angular momentum.
Moment of inertia (I) is the resistance to rotational change, while angular velocity (ω) is the rate of rotation. Angular momentum (L) is the product of these two: L = Iω.
Compare rigid and non-rigid systems in the context of angular momentum.
Rigid system: Moment of inertia is constant unless external forces act. Non-rigid system: Moment of inertia can change due to changes in shape or mass distribution, affecting angular speed.