Chapter 15. Fluids

Physics, 6th Edition

Chapter 15. FLUIDS
Density
15.1. What volume does 0.4 kg of alcohol occupy? What is the weight of this volume?

ρ=

m ; V

V=

m 0.4 kg = ; ρ 790 kg/m 2

V = 5.06 x 10-4 m3 W = 3.92 N

W = DV = ρgV = 790 kg/m3)(9.8 m/s2)(5.06 x 10-4 m3);

15-2. An unknown substance has a volume of 20 ft3 and weighs 3370 lb. What are the weight density and the mass density? D= W 3370 lb = ; D = 168 lb/ft3 V 20 ft 3

ρ=

D 168 lb/ft 3 = ; g 9.8 m/s 2

ρ = 5.27 slugs/ft3

15-3. What volume of water has the same mass of 100 cm3 of lead? What is the weight density of lead? First find mass of lead: m = ρV = (11.3 g/cm3)(100 cm3); m = 1130 g Now water: Vw = m 1130 g = = 1130 cm3 ; Vw = 1130 cm3 …ver más…

A water-pressure gauge indicates a pressure of 50 lb/in.2 at the foot of a building. What is the maximum height to which the water will rise in the building? P = Dh; h= P (50 lb/in.2 )(144 in.2 /ft 2 ) = ; D 62.4 lb/ft 2 ) h = 115 ft

The Hydraulic Press
15-15. The areas of the small and large pistons in a hydraulic press are 0.5 and 25 in.2, respectively. What is the ideal mechanical advantage of the press? What force must be exerted to lift a ton? Through what distance must the input force move, if the load is lifted a distance of 1 in.? MI = [1 ton = 2000 lb ] Fi = 2000 lb ; 50 si = 50 in. Fi = 40.0 lb

Ao 25 in.2 ; M = 50 I = Ai 0.5 in.2

si = MI so = (50)(1 in.);

15-16. A force of 400 N is applied to the small piston of a hydraulic press whose diameter is 4 cm. What must be the diameter of the large piston if it is to lift a 200-kg load? Fo Ao d o2 = = ; Fi Ai di2 do = di Fo (200 kg)(9.8 m/s 2 ) = (4 cm) ; Fi 400 N

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Chapter 15. Fluids do = 8.85 cm

Physics, 6th Edition

15-17. The inlet pipe that supplies air pressure to operate a hydraulic lift is 2 cm in diameter. The output piston is 32 cm in diameter. What air pressure (gauge pressure) must be used to lift an 1800-kg automobile. Pi = Po ; Pi = Fo (1800 kg)(9.8 m/s 2 ) = ; Ao π (0.16 m) 2 Pi = 219 kPa

15-18. The area of a piston in a force pump is 10 in.2. What force is required to raise