HW_14_Solutions_F05

# HW_14_Solutions_F05 - Physics 112 HW#14 Solutions...

This preview shows pages 1–3. Sign up to view the full content.

- 1 - Physics 112 - HW #14 Solutions Spring 2005 13-54 [Driven Oscillations] If k = m ω d , then A 1 = F max (k - m ω d 2 ) 2 + b 1 2 ω d 2 = F max b 1 ω d (a) A = F max (3b 1 ) ω d = A 1 3 (b) A = F max (b 1 /2) ω d = 2A 1 13-90 [L-rod Oscillator] The CM of the swinging system (two rods combined) is located a distance from the pivot equal to: d = L/2 2 = L 2 2 . The system's moment of inertia about the pivot point is: I = 1 3 mL 2 + 1 3 mL 2 = 2 3 mL 2 = 1 3 ML 2 [where M = 2m is the total mass of the system] So the freq. of its SHM oscillation is: f = 1 2 π Mgd I f = 1 2 π Mg L 2 2 1 3 ML 2 = 1 2 π 3g 2 2L 14.11 [Diving Bell] (a) Gauge pressure p = ρ g h = (1.03 x 10 3 kg/m 3 )(9.81 m/s 2 )(250 m) = 2.52 x 10 6 Pa (b) Force on window F = p A = p π r 2 = (2.52 x 10 6 Pa)(3.142)(0.150 m) 2 = 1.78 x 10 5 N CM d L/2 L/2

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
- 2 - 14.54 [Hot Air Balloon] Total weight of balloon + gases inside is W = ρ g V g + 900 N + 1700 N + 3200 N = ρ g V g + 5800 N Bouyancy force is equal to the weight of air displaced by the balloon. F b = ρ a V g = (1.23 kg/m 3 )(2200 m 3 )(9.81 m/s 2 ) = 2.655 x 10 4 N For balloon to be just able to lift, F b = W, so 2.655 x 10 4 N = ρ g V g + 5800 N ρ g V g = 2.075 x 10 4 N ρ g = 2.075 x 10 4 N (2200 m 3 ) (9.81 m/s 2 ) = 0.961 kg/m 3 14.64 [Block and Beaker on Scales] (a) The liquid in the beaker is pushing up on the block with force f b = ρ l V block g, the bouyant force. So the block must be pushing DOWN on the liquid with a force of the same magnitude (N’s 3 rd law.) Then the reading on balance E, times g, is the weight of the liquid plus the beaker, plus (the
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 6

HW_14_Solutions_F05 - Physics 112 HW#14 Solutions...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online