AP CollegeBlamed w : ( 1 ) + 1 2 ( 2 ) ( 4 2 ) Scoring Guide Unit 5.2 Rotational Kinematics (A) 4 radians (B) 16 radians C) 20 radians 8 = 36 D) 24 radians (E) 36 radians V . 8. A disk initially at rest is acted upon by a constant net torque of T. The disk spins for a period of t seconds and rotates an angular distance of 0. The same disk is brought to rest. The disk is now acted upon by a constant net torque of 27. The disk spins for the same period of t seconds. What is the new angular distance the disk rotates? (A) 40/2 (B) V240 C) Ae (D) 2 40 9. A windmill is spinning because of the nonuniform force of the wind. The windmill is originally spinning at a speed of wo , and a crosswind slows it with an angular acceleration of - Aws. What will be the angular speed of the windmill at time t = T'? (A) 1+ATwo (B) Woe-AT (C) wo(1 - e-AT) (D) Wo + AT (E) Wo - Aw-T . A rotating object has an angular position represented by 0 = A + Bt + Ct , where A , B , and C are constants. A student wants to represent a different rotating object that has twice the angular speed at every moment. To write the new function, the student could (A) double B only ( A + Bt + (t' )- ( B + 2 ( t > > (B) double C only W = C) double both A and B t t t D) double both A and C (E) double both B and C = 213 + yet Only B andAP CollegeBoard AP PHYSICS C: MECHANICS Scoring Guide Unit 5.2 Rotational Kinematics 1. A particle moves in the xy-plane with coordinates given by x = A cos wt and y = A sin wt, where A = 1.5 meters and w = 2.0 radians per second. What is the magnitude of the particle's acceleration? (A) Zero (B) 1.3 m/$2 (C) 3.0 m/s2 (D) 4.5 m/s2 (E) 6.0 m/s2 2. V . A disk is free to rotate about an axis perpendicular to the disk through its center. If the disk starts from rest and accelerates uniformly at the rate of 3 radians/s for 4 s, its angular displacement during this time is (A) 6 radians t B) 12 radians AD = ot 2 ( 2 ) ( 4 ) 2 (C) 18 radians D) 24 radians = 24 padians (E) 48 radians R A wheel of 0.5 m radius rolls without slipping on a horizontal surface. The axle of the wheel advances at constant ( w velocity, moving a distance of 20 m in 5 s. The angular speed of the wheel about its point of contact on the surface is W (A) 2 radians . s-1 20 = vit (B) 4 radians . s-1 V : (5 S (C) 8 radians . s-1 (D) 16 radians . s WE = 8 vi = y (E) 32 radians . s-1 Vi =0 of 20 1. A turntable that is initially at rest is set in motion with a constant angular acceleration a. What is the angular velocity of the turntable after it has made one complete revolution? (A) V2a DO = zat2 (B) V2Ta W t (C) VATO - a (D) 20 (E) 4TO 2 w = Lat Do = witt z atz AP Physics C: Mechanics Page 1 of 5-1 = 0.93 Hz Scoring Quick Unit 5.2 Rotational Kinematics 5. A rotating platform with a radius of 2.0 m makes one complete turn every 3.0 s. The angular velocity of the platform is most nearly (A) 2.1 rad/s (B) 1.5 rad/s 2 - 7 . 0 3 3 = 2.09 2 2 . 1 rad/s (C) 1.0 rad/s (D) 0.70 rad/s (E) 0.30 rad/s The bar shown above is pivoted about one end and is initially at rest in a vertical position. The bar is displaced slightly and as it falls it makes an angle (@ with the vertical at any given time, as shown above. 6. Which of the following graphs best represents the bar's angular velocity a as a function of time? Page 2 of 5 AP Physics C: Mechanics Scoring Guide Unit 5.2 Rotational Kinematics (A) - Time (B) -Time (9) - Time (D) X - Time (E) TimeF R Axis of Rotation A solid disk of mass Aradius R and rotational inertif I is free to rotate about a fixed frictionless axis that is perpendicular to the disk through its center, as shown above. A force of constant direction and constant magnitude F is exerted on the disk. 11. If the disk is moving clockwise with an angular speed of 5.0 Led with angular acceleration of magnitude 1.3 rad What is the angular speed of the disk three seconds later? (A) 1.1 rad It will increase by 1.3 rad/s (B) 3.9 rad every second so S+ 1.3 - first sec (C) 5.0 rad 6 . 3+ 1.3 -7 second sec (D) 8.9 rad 7.6 + 1.3 third sec (E) 16 rad 8.8 rad /s 12. Two people, A and B, are riding a large horizontal rotating platform. The platform rotates around its center. If person A is twice as far from the center as person B, which of the following statements is true? (A) Both people have the same angular speed, but person B has a greater tangential speed. (B) Both people have the same tangential speed, but person B has a greater angular speed. C) Both people have the same angular speed and tangential speed (D) Both people have the same angular speed, but person A has a greater tangential speed. (E) Person A has both a greater angular speed and a greater tangential speed. AP Physics C: Mechanics Page 5 of 5