Problems For each problem show all work by filling in the boxes: identify the known and unknown, write the correct formula, substitute & solve, write answer in correct units. 21. A pendulum swings to-and-fro (back-and-forth) 12 times in 8 seconds. What is its frequency? Known & Unknown Formula Substituted Formula & Solve Answer w/ correct units t = 8sec 8 /12 sing 12 times 22. In the previous problem, what is the period? Known & Unknown Formula Substituted Formula & Solve Answer w/ correct units. t = 8 sec 12 frequency swing 12 times 2- 998 5 Hy 0. 607 23. A 3 g coin rotates at the edge of a turntable (radius = 40 cm) once every 4 s. What is its velocity? Known & Unknown Formula Substituted Formula & Solve Answer w/ correct units. 30 (m = 0.03 m 2( 70) 10-03 ) tsusec 0.047/m/s 4 M = 39 24. A 3 g coin rotates at the edge of a turntable (radius = 30 cm) once every 4 s. What is its centripetal acceleration? Known & Unknown Formula Substituted Formula & Solve Answer w/ correct units m = 39 70( 0.03) 3 63-83m/s r= 30 (m = o.03n 4 =0.047 DU47 t= 4sec 25. A 3 g coin rotates at the edge of a turntable (radius = 30 cm) once every 4 s. What is the force of friction? Known & Unknown Formula Substituted Formula & Solve Answer w/ correct units. m = 39 100 ( 6 ) 100 (0. 03 Y= 30(m = 0-03m m 3 t= 4 sec X