2Which is faster? The horse on the outside or the horse on the inside?
3Merry-Go-RoundSame rotational speed for all animals on the Merry-Go-Round because they are attached rigidly.Animals further out have a greater linear speed.
4Rotational Speed Also called Angular Speed Circular Speed ω (lower case Omega Ω)
5Linear Speed (v)Also calledTangential Speedv or vT
6Describe Earth’s motion using the words rotate, revolve, and axis. Axis: Straight line around which rotation takes place.Days on Earth.Rotation: Spin. Axis is located within the object.Days on Earth.Revolution: Object turns about an external axis.Earth years.
7Frequency vs. PeriodPeriod (T)- The time it takes for one full rotation or revolution of an object in seconds.Frequency (f)- The number or rotations or revolutions per unit time, measured in Hertz (Hz)
8Revolution Lab Questions: Challenges: 1) How is radius related to revolution speed?2) What happens when you are spinning the stopper at a constant rate and then suddenly pull down on the string? Why does this happen?3) Does a spinning object accelerate? If so, what is the direction of acceleration?Challenges:1) Spin a rubber stopper above your head at several different lengths to answer the question above. Do multiple trials.2) Graph your data to help find the mathematical relationship between radius and revolution speed.
13What happens when you are spinning the stopper at a constant rate and then suddenly pull down on the string? Why does this happen?It spirals in because you apply a constant force inward. You reduce the radius.
14what is the direction of acceleration of an object in uniform circular motion?
15what is the direction of acceleration of an object in uniform circular motion? There is a radial component of acceleration responsible for the constant direction change, and a tangential component of acceleration which results in an increase or decrease in tangential speed.
16Describe the path of the stopper IF you were to cut the string between the tube and the bottom weight
17Centripetal Force FcA force of some kind is required to maintain circular motion. Why?Any force that causes an object to follow a circular path is called a centripetal force.Centripetal means “center-seeking”Always acts inwards
18Centripetal Acceleration ac Tangential VelocityRadius
23How long will it take to land? Review ProblemsDerive the expression (fully simplified) that will determine the time it will take for a projectile launched on flat ground to reach its maximum height.How long will it take to land?
24Review Problems What is the range R? 750m 375m 105m 210m 150m c) 105m v0x=15m/sh=250mRWhat is the range R?750m375m105m210m150mc) 105m
25What is the speed of the object when it hits the ground? Review Problemsv0x=15m/sh=250mRWhat is the speed of the object when it hits the ground?72m/s15m/s150m/s70m/s21m/sa) 72m/s
26Review ProblemsA (peak)v0What is the direction of the acceleration vector and velocity vector at point A?0m/s2 and 0m/s d) a va v e) a m/sa vc)
27Review ProblemsA very agile physics student is standing on one of those spinny things in a playground without slipping. Which force provides the student’s centripetal acceleration?Normal Force d) Centrifugal ForceWeight e) NoneFriction on shoes f) Abnormal forcec)
28Review Problems Two quarters are on a spinning turntable. One head side up and one tail side up.Heads is at a distance R/2 from the center.Tails is a distance R from the center.What is the ratio of accelerations (ah/at)?2/11/212^(1/2)2^-(1/2)b)
29Review ProblemsAB (along rope)CCACBED (tangent to curve)For the pendulum on the left, which vector on the right possibly shows the direction of acceleration at point A?
30Review ProblemsABACACDBEFor the pendulum on the left, which vector on the right shows the direction of acceleration at point B?
31Review ProblemsθLFor the conical pendulum above, find a fully simplified expression for the period in terms of theta, L, g, and other constants.
32Review Problems We need an equation with T in it! What is r? θWe need an equation with T in it!rWhat is r?Ok, so what is v?Take it easy, make an FBD.