# Mechanics II

 What are the three types of motion? There is a special point in a system or object called the ______ ____ _____, that moves as if all the mass of the system is concentrated at that point. The system will move as if an external force were applied to a _______ ______ of mass M (where will this be located?) center of masssingle particle center of mass For a simple object such as a sphere, block, or cylinder, whose density is constant (homogeneous), the center of mass is at the _______ _______. Where does the center of mass tend to be for irregular or complicated objects? geometric center Tends to lie closer to the heavier objects or particles that make up the entire object What is the formula for the center of mass for both x and y coordinates  Gravity doesn't act at a single point on an object, it pulls downward on _____ _____ that makes up the object. However, the gravitational force can be calculated by assuming that the _____ _____ of gravity acts at a single special point on the object called its ______ _____ _____ every particlenet force center of gravity Any object free to rotate about a pivot will come to rest with its center of gravity directly ______ the pivot. Define the center of gravity directly belowCenter of gravity: the average position of the gravitational forces on all parts of the object What is the difference between center of gravity and center of mass? Center of mass determines trajectory of objects, the object will move as if all of its mass was concentrated at that point.Center of gravity determines downward pull of gravitational force, gravity will act on every particle on the object and this will be most apparent where the object has the highest concentration of particles   Uniform circular motion occurs when an object moves in a _____ path with a _____ speed, v. If speed is constant, what about acceleration? circularconstantSpeed is constant = magnitude of velocity is constant, but direction of velocity is different at any time so acceleration is never zero, a ≠ 0*This change in velocity is related to an acceleration The velocity vector is always ______ to the path of the object and the velocity is ______ to the radius of the circular path tangentperpendicular The period, T, is the time interval required for one complete revolution. What is the formula for both speed and period in this context speed = perimeter/periodT = 2πr/v A rigid object is one that is _________. The relative locations of all particles making up the object remain ______. When a rigid body is rotating about a fixed axis, every particle on the object rotates about that axis through three factors that remain the same (name them) nondeformableconstant same angular displacement, angular speed and angular acceleration Polar coordinates are convenient to use to represent the position of P (or any other point). P is located at (__,__) (r,θ)*θ is measured counterclockwise from the reference line Define angular position (state the S.I. unit and how to convert from degrees to radians) Angular position: the angular position of the rigid object is the angle  between the reference line on the object and the fixed reference line in space As the particle moves in uniform circular motion, the only coordinate that changes is θ. As the particle moves through θ, it moves through an arc length s = ____ and Δθ = _____ s = rΔθΔθ = θf - θi State the formula for average angular velocity of a particle For a particle moving with uniform circular motion, ω is ______. Define angular speed and state the units constantAngular speed: absolute value of the angular velocity (scalar quantity, no direction)S.I. Units: rad/s or s-1 (since radians have no dimensions)*also measured in rev/s and rpm What are the rules for knowing if angular velocity will be < or > 0? Since particles move in a circular motion, translational velocity is always _____ to the path (_____ velocity) s (_____ ____) = ___ What is the formula for tangential aka linear velocity tangent (tangential velocity)  B. Angular velocity/speed is the same between a and b *Don't mix up with linear velocity/speed The acceleration is always _______ to the path of motion. It always points to the _______ of the circle of motion. This acceleration is called the _______ ________ perpendicularcentercentripetal acceleration What is the formula/magnitude of the centripetal acceleration vector? What is its direction? Angular acceleration α measures how rapidly the ______ ______ is changing: What is the formula for average angular acceleration, αavg: angular velocity State the formula  and units for instantaneous angular acceleration, α: When is angular acceleration positive and when is it negative? Consider a particle moving to the right along a curved path where the velocity changes both in direction and in magnitude. In this case, there would be both _______ _______ and _______ _______ centripetal acceleration and tangential acceleration What is the formula for: Total acceleration Tangential acceleration Radial acceleration  *which direction does each unit vector point?   All points on the rigid object will have the same ______ speed, but not the same _______ speed. All points on the rigid object will have the same ________ acceleration, but not the same ________ acceleration. The tangential quantities depend on the _______ which is not the same for all points on the object angular speedtangential speedangular acceleration tangential accelerationradius State the 4 rigid body (constant angular acceleration) formulas  *Bonus: state the 4 particle under constant acceleration formulas State the formula for: 1) Angular displacement at constant angular speed 2) Change in angular velocity at constant angular acceleration  *Bonus: state the equivalent linear motion formulas 1) Δθ = ωΔt | Δx = vΔt2) Δω =αΔt | Δv = αΔt What is the formula for: angular position angular velocity  tangential acceleration θ = s/r (*s = arc length)ω = v/r (*v = tangential speed)at = αr A particle of mass m moving at constant speed v around a circle of radius r must have an acceleration, ac = ___ = ___ pointing toward the ______ of the circle ac = v2/r = rω2center The net force associated with the centripetal acceleration is the centripetal force. This force is a _____ force, not a physical force. Newton's second law along the radial direction gives? net force This centripetal force causes a change in the direction of the ______ ______. If the force vanishes, the object would move in a straight-line path ______ to the circle velocity vectortangent Strategy for solving Circular Dynamics Problems: (6-story) What are the 5 typical cases in Circular Dynamics Horizontal circular motion with a stringUnbanked curve motion Banked curve motion Loop-the-loop: vertical circular motion without tied to a stringVertical circular motion with a string Explain the horizontal circular motion with a string:  A mass is tied to a cord or string which generates _______ force. Only that force is along the _______ direction (state the newton's 2nd law). What can be said about this force reaching its maximum limit? Tension forceradial directionΣFr = T = mac = mv2/rOnce T > maximum limit: 1) The cord or string will break. 2) No more circular motion3) v = vtang = constant, a straight line path Explain Unbanked curve motion (car) ______ friction prevents a car from skidding radially outward when turning an unbanked curve.  State Newton's second law Static frictionΣFr = fs = mac = mv2/r*Keep in mind this is the upper limit of static friction so you'll be asked to find the maximum speed limit Explain Banked curve motion (car): If the path is nearly negligible, then can you can't use ______ force to make the the turn. Instead, the _____ force prevents the car from skidding. State Newton's 2nd Law The _____ of the banked curve determines the maximum speed friction forceNormal force ΣFr = Nr = mv2/rangle Explain the Loop-the-loop: Vertical circular motion without being tied to a string: The ______ (state the min possible value) and component of ________ force are along the radial direction, depends on the location of the object in the loop. State Newton's 2nd law normal force (N ≥ 0)gravitation force  Explain vertical circular motion with a string:  Similar to the loop-the-loop, but involve ______ instead of ______ force. State Newton's 2nd law Which force has an upper breaking limit? Tension and not normal force What is the max walking speed formula? A force that seems to push an object to the outside of a circle is called a ________ force. E.g. When you're making a turn, you feel there is a force pushing your body outward. However, your body is just trying to move forward in a straight line while the car is making a turn. So what can be said of this outward force? centrifugal forceIt doesn't exist Provide free body diagram and newton's 2nd law for riding a Ferris wheel (at the top and at the bottom)  B.   Centripetal acceleration: They are all the same because speed is constant and there is no change in radius Normal force: A = E > B = D > CApparent weight: A = E > B = D > C Authorchikeokjr ID343626 Card SetMechanics II DescriptionMechanics Pt II Updated2018-11-22T19:35:41Z Show Answers