Chapter 7: Rotational Motion

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

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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

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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

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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

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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

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