A given alloy contains 20% copper and 5% tin. How many pounds of copper and of tin must be melted with 100 lb of the given alloy to produce another alloy analyzing 30% copper and 10% tin? All percentages are by weight.
A. 20.5 lb copper and 4.5 lb tin
B. 17.5 lb copper and 7.5 lb tin
C. 19.5 lb copper and 5.5 lb tin
D. 18.5 lb copper and 6.5 lb tin
A nutritionist in a hospital is arranging special diets that consist of a combination of three basic foods. It is important that the patients on this diet consume exactly 310 units of calcium, 190 units of iron, and 250 units of vitamin A each day. The amounts of these nutrients in one ounce food are given in the following table.
Units Per Ounce
How many ounces each food must be used to satisfy the nutrient requirements exactly?
A. 6 ounces of Food A, 5 ounces of Food B and 3 ounces of Food C
B. 3 ounces of Food A, 5 ounces of Food B and 6 ounces of Food C
C. 6 ounces of Food A, 3 ounces of Food B and 5 ounces of Food C
D. 5 ounces of Food A, 3 ounces of Food B and 6 ounces of Food C
A temporary earth retaining wall consists of wooden plank driven vertically into the ground. The wall is designed to resist 2.4 m height of soil.
Cross-sectional dimensions of the plank = 300 mm wide × 75 mm thick
Allowable bending stress of the plank = 10.4 MPa
Allowable shear stress of the plank = 0.8 MPa
Unit weight of retained soil = 17.3 kN/m3
Active earth pressure coefficient = 1/3
1. Calculate the maximum flexural stress.
A. 12.7 MPa
C. 8.6 MPa
B. 14.2 MPa
D. 10.1 MPa
2. Calculate the maximum shear stress.
A. 1.11 MPa
C. 0.99 MPa
B. 0.33 MPa
D. 0.77 MPa
3. Calculate the minimum thickness of the plank to prevent failure.
A catapult is placed 100 ft from the castle wall, which is 35 feet high. The soldier wants the burning bale of hay to clear the top of the wall and land 50 feet inside the castle wall. If the initial velocity of the bale is 70 feet per second, then at what angle should the bale of hay be launched so that it travel 150 feet and pass over the castle wall. Use g = 32 ft/sec2.