E. Circular Motion II

Homework

8.1 Rigid Bodies and Rotations

5, 10, 13

10: v_cm = rw solve for w

13: a = a_t/r solve for a. Next, w² = w_o² + 2aq where you solve for q

8.2 Torque, Equilibrium, Stability

14, 18, 19, 24, 30, 31

14: Look at figure 8.5 c on p. 256 and you’ll see SF = 0 but the St doesn’t = 0

18: When the force is applied ^ to the length of the wrench, minimum force is required and the lever arm equals the length of the wrench. At q = 90^o, r_^= 0.15 m

t = Fr_^ solve for F

19: In this case, r_^ = 0.15 sin 30. Use formula from 18 and again solve for F.

24: St = 0. Don’t forget that to find distances you must subtract from the designated pivot point.

30: see example 8.5 on p. 259

31: Choose where the string acts as the axis and work from the bottom up. Realize that St must = 0 since they aren’t rotating.

Even Answers:

10: 1.7 rad/s

14: b

18: 1.7 x 10² N

24: a: 83.3 cm b. 62.5 g

30: 2.1 x 10² N