1/How much work is done by the motor in a CD player to make a CD spin, starting
ID: 2102891 • Letter: 1
Question
1/How much work is done by the motor in a CD player to make a CD spin, starting from rest? The CD has a diameter of 12.0 cm and a mass of 16.2 g. The laser scans at a constant tangential velocity of 1.29 m/s. Assume that the music is first detected at a radius of 19.9 mm from the center of the disk. Ignore the small circular hole at the CD's center.
2/A mechanic turns a wrench using a force of 27.5 N at a distance of 18.9 cm from the rotation axis. The force is perpendicular to the wrench handle. What magnitude torque does she apply to the wrench?
3a/As shown in the figure below, a 41.5-N force is applied to the outer edge of a door of width w = 1.26 m in such a way that it acts perpendicular to the door. Calculate the torque.
b/Now, the 41.5-N force is applied to the outer edge of that door in such a way that it acts at an angle of ? = 42.2
Explanation / Answer
1) w when music is detected = 1.29 x 1000/19.9 = 62.824 I = (16.2 x .06^2)/2 = .02916 Energy = Iw^2/2 = 57.545 J 2) Torque = R X F = 27.5 x 18.9/100 = 5.1975 Nm 3) a) Torque = 41.5 x 1.26 = 52.29 Nm b) Torque = 41.5 x 1.26 x sin42.2 = 35.12 Nm c) Torque = 0 4) a) l + r = (77.9 + 20.5)g centre of mass is located at .30875 m left of centre, so balancing Torque: 98.4 x 1.94125 = r x 4.5 => r = 42.448 N => l = 55.95 N => by left cable = 55.95 N b) by right cable = 42.448 N 6) 2.86 x 12.6 = 1.55 x w => w = 23.24 rad/s
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.