26. A block of wood weighs 42.5 lb in air. A vertical force of 30 lb is required to keep the block submerged in water. Compute the unit weight and specific gravity of the wood.
27. A block of metal weighs 42.5 lb in air and 30 lb when suspended in water. Compute the unit weight and the specific gravity of the metal.
28. The inverted timber U-frame shown in Fig.H consists of a horizontal 12-by-12-in. timber 12 ft long, to the ends of which are attached two vertical 12-by-12-in. timbers 10 ft long, extending downward through openings in the bottom of a tank of water. Neglecting friction in the guides at the openings, determine the amount and direction (up or down) of the forces F, F required to hold the frame in equilibrium. The timbers weigh 40 lb per cu ft. Water surface is 3' diameter.
Sea water w = 64.0
Fig.H
Fig.J
29. The solid cylindrical plug A in Fig.J is 3 ft in diameter and 2 ft high. It is made of concrete weighing in air 150 lb per cu ft. With fresh water on one side and sea water on the other as shown, and neglecting friction in the guides, find the vertical force F required to hold the plug in position.
30. The solid cylindrical plug A in Fig.K (sp gr 0.80) is 2 ft in diameter and 2 ft high. With oil on one side and sea water on the other as shown, and neglecting friction in the guides, find the required weight of the plug so that it will be in equilibrium.
Fig.L
31. A 6-in. by 6-in. timber, 20 ft long weighing 40 lb per cu ft, is hinged at one end and held in a horizontal position by an anchor at the other end as shown in Fig. L. If the
