Rotational Motion
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22 terms
Terms | Definitions |
|---|---|
 Circular Motion | motion with constant radius of curvature caused by acceleration being perpendicular to velocity |
| Axis | the straight line around which rotation occurs |
| Rotate (spin) | circular motion around an internal axis (e.g. the Earth rotates to cause a cycle of day and night) |
| Revolve | circular motion around an external axis (e.g. the moon revolves around the Earth) |
| Linear Speed (translational speed) | the distance travelled by an object within a specified amount of time; linear speed is directly proportional to the distance an object is from the center of a rotational platform |
| Rotational Speed (angular speed) | the speed with which an object moves through an angle for every unit of time; units: RPM (revolutions per minute), rad/s, θ/s |
| Period | the amount of time it takes to complete one cycle (1 revolution) |
| Centripetal Acceleration | Newton's First Law states that a body in motion stays in motion at a constant speed and in a straight line unless acted upon by a net force; therefore, a force must be pulling inward on an object moving in a circular path in order to prevent it from moving in a straight path. |
| Centripetal ("Center-Seeking") Force | any force that acts at a right angle to a moving object's path and results in circular motion |
| Centrifugal ("Center-Fleeing") Force | This force is not an actual force; it is a fictitious force that seems to pull outwards on an object on a circular path. This effect is due to inertia, or the tendency for a moving object to follow a straight path. |
| Simulated Gravity | Centrifugal force can simulate gravity because from within a rotating frame of reference, there seems to be a centrifugal force directed outward. |
| Formula for Centripetal Acceleration | a = v^2/r = 4rπ^2/T where v = velocity, r = radius, T = period |
| Formula for Centripetal Force | F = ma = m(v^2/r) where m = mass, a = centripetal acceleration, v = velocity, r = radius |
| Torque | the tendency of a force to rotate an object about an axis (force x lever arm) |
| Rotational Inertia | the resistance of an object to changes in its rotational state of motion |
| Rotational Velocity (angular velocity) | the rate of rotation around an axis (expressed in radians or revolutions per second/per minute) |
| Pendulum | an object hanging from a fixed point which, when pulled back and released, is free to swing back down by gravity and inertia |
| Formula for Torque | Torque = r x F where r = the displacement vector, F = the force vector |
| Formula for Rotational Inertia | I = mr^2 where m = mass, r = distance, I = rotational inertia |
| Angular Momentum | the quantity of rotation of a body, which is the product of its moment of inertia and its angular velocity |
| Law of Conservation of Momentum | Iiωi=Ifωf where li = initial momentum, ωi = initial angular speed, lf = final momentum, and ωf = final angular speed |
| Formula for Angular Momentum | L = Iω where L (angular momentum) translates to linear momentum (p), and I (moment of inertia) translates to mass (m), and ω (angular velocity) translates to velocity (v). This is the translation from rotational (circular world) terms to linear terms (linear world). |
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