Chapter 7: Rotational Motion

Watts

Watts

Power is the rate at which work is done or energy is transferred and is measured in ________.

different application

Parallel forces act in the same direction on an object but have ________ points.

Torque

________ is used to describe the motion of objects that rotate around a fixed axis, such as a wheel or a gear.

Inertia

________ can be thought of as a measure of an object's resistance to a change in its state of motion and is related to the object's energy and momentum.

external torque

A(n) ________ can change the angular momentum of an object or system, causing it to rotate faster or slower, or to change direction.

circular motion

The frequency of an object in ________ is the number of rotations per unit time and is equal to the inverse of the period.

property of matter

It is a(n) ________ that causes an object to maintain its current velocity and direction of motion unless acted upon by an external force.

Torque

________ is the measure of a force's ability to cause rotational motion and is equal to the force times the lever arm (the distance between the force and the axis of rotation)

Rigid body equilibrium

zero translational (linear) or angular acceleration 1. sum of external forces = 0 N 2. sum of externally applied torques = 0 Nm *can be in static or dynamic equilibrium

center of mass

average location of mass - Fg is not considered - CM = center of gravity when there is a uniform gravitational field (ex: on earth, in classroom) - when solving for center of mass, solve for x and y coordinates individually

center of gravity

Fg considered- finding torque produced by Fg: weight of the object can be considered to be concentrated at a single point

moment of inertia (I)

resistance to a change in the rotational state of moment of an object- resistance to angular acceleration- depends upon distribution of mass and shape

torque and angular acceleration

when a rigid body is subjected to a net torque (t≠0), it undergoes angular acceleration *relationship analogous to Newton's second law

Arc length

S = rθ (m) = (m)(rad)

Period (T)

time it takes to complete a full rotation on a closed path = 1/frequency (f)

Conservation of energy

conservative forces only → all conservative forces should be included (TKE + RKE +PEG)i = (TKE + RKE +PEG)f the principle that the amount of energy in a system is constant

rotational kinematic variables

angular displacement (θ) - change in theta angular velocity (ω) - angular displacement over time angular acceleration (α) - change in angular velocity over time

angular momentum - right hand rule

fidget spinner → angular momentum keeps the fidget spinner upright, torque causes procession spinning on platform → if the wheel is spinning towards the left, platform is spinning towards the right