College Physics 2e

# Chapter 10

### Problems & Exercises

1.

$ω = 0 . 737 rev/s ω = 0 . 737 rev/s$

3.

(a) $−0.26 rad/s2−0.26 rad/s2$

(b) $27rev27rev$

5.

(a) $80 rad/s280 rad/s2$

(b) 1.0 rev

7.

(a) 45.7 s

(b) 116 rev

9.

a) $600 rad/s2600 rad/s2$

c) 21.0 m/s

10.

(a) 0.338 s

(b) 0.0403 rev

(c) 0.313 s

12.

$0.50 kg ⋅ m 2 0.50 kg ⋅ m 2$

14.

(a) $50.4 N⋅m50.4 N⋅m$

(b) $17.1 rad/s217.1 rad/s2$

(c) $17.0 rad/s217.0 rad/s2$

16.

$3 . 96 × 10 18 s 3 . 96 × 10 18 s$

or $1.26 × 10 11 y 1.26 × 10 11 y$

18.

$I end = I center + m l 2 2 Thus, I center = I end − 1 4 ml 2 = 1 3 ml 2 − 1 4 ml 2 = 1 12 ml 2 I end = I center + m l 2 2 Thus, I center = I end − 1 4 ml 2 = 1 3 ml 2 − 1 4 ml 2 = 1 12 ml 2$

19.

(a) 2.0 ms

(b) The time interval is too short.

(c) The moment of inertia is much too small, by one to two orders of magnitude. A torque of $500 N⋅m500 N⋅m$ is reasonable.

20.

(a) 17,500 rpm

(b) This angular velocity is very high for a disk of this size and mass. The radial acceleration at the edge of the disk is > 50,000 gs.

(c) Flywheel mass and radius should both be much greater, allowing for a lower spin rate (angular velocity).

21.

(a) 185 J

(b) 0.0785 rev

(c) $W=9.81 NW=9.81 N$

23.

(a) $2.57×1029 J2.57×1029 J$

(b) $KErot=2.65×1033 JKErot=2.65×1033 J$

25.
$KE rot = 434 J KE rot = 434 J$
27.

(a) $128 rad/s128 rad/s$

(b) $19.9 m19.9 m$

29.

(a) $10.4 rad/s210.4 rad/s2$

(b) $net W=6.11 J net W=6.11 J$

34.

(a) 1.49 kJ

(b) $2.52×104 N2.52×104 N$

36.

(a) $2.66×1040kg⋅m2/s2.66×1040kg⋅m2/s$

(b) $7.07×1033kg⋅m2/s7.07×1033kg⋅m2/s$

The angular momentum of the Earth in its orbit around the Sun is $3.77×1063.77×106$ times larger than the angular momentum of the Earth around its axis.

38.

$22 . 5 kg ⋅ m 2 /s 22 . 5 kg ⋅ m 2 /s$

40.

25.3 rpm

43.

(a) $0.156 rad/s0.156 rad/s$

(b) $1.17×10−2 J1.17×10−2 J$

(c) $0.188 kg⋅m/s0.188 kg⋅m/s$

45.

(b) Initial KE = 438 J, final KE = 438 J

47.

(b) Initial KE = 22.5 J, final KE = 2.04 J

(c) $1.50 kg⋅m/s1.50 kg⋅m/s$

48.

(a) $5.64×1033kg⋅m2/s5.64×1033kg⋅m2/s$

(b) $1.39×1022N⋅m1.39×1022N⋅m$

(c) $2.17×1015N2.17×1015N$ Do you know how you learn best?