Looks Fam Flashcards
(11 cards)
Which part has the greater stress?
I. An aluminum bar of 2.46 cm x 3.07 cm cross section, under
a load of 7640 kg
II. A steel bar whose cross-sectional diameter is 1.28 cm,
under a 5000-kg load.
A. I has a greater stress at 480 MPa
B. II has a greater stress at 380 MPa
C. I has a greater stress at 380 MPa
D. II has a greater stress at 480 MPa
B. II has a greater stress at 380 MPa
A 5.08 cm gage length is marked on a copper rod. The rod is strained so that the gage marks are 5.77 cm apart. Calculate the strain.
A. 16.5% B. 13.5% C. 15.5% D. 14.5%
B. 13.5%
If the average modulus of elasticity of the steel used is 205,000 MPa, how much will a wire 2.5 mm in diameter and 3 meters long be deformed when it supports a load of 4900 N?
A. 1.5 cm B. 2.5 cm C. 3.5 cm D. 4.5 cm
A. 1.5 cm
NOV 2022. A copper wire has a nominal breaking strength of 300 MPa and a reduction of area of 77%. Calculate the true tensile strength.
Hint: breaking load/true area
A. 1200 MPa B. 1250 MPa C. 1300 MPa D. 1350 MPa
C. 1300 MPa
A copper wire has a nominal breaking strength of 300 MPa and a reduction of area of 77%. Calculate the true strain 𝜀𝑡𝑟 at the point of fracture.
Hint: The instantaneous strain 𝑑𝜀 is equal to 𝑑𝑙/𝑙
A. 174% B. 274% C. 247% D. 147%
D. 147%
NOV 2022. An aluminum wire is stressed 34.5 MPa in tension. What temperature increase is required to change its length by the same amount?
[Note that for aluminum, E = 70 GPa and 𝛼 = 22.5 x 10-6/°C] A. 17°C B. 22°C C. 12°C D. 27°C NOV 2022. An aluminum wire is stressed 34.5 MPa in tension. What temperature increase is required to change its length by the same amount?
[Note that for aluminum, E = 70 GPa and 𝛼 = 22.5 x 10-6/°C]
A. 17°C B. 22°C C. 12°C D. 27°C
B. 22°C
A stainless steel plate 0.4 cm thick has a circulating hot water on one side and a rapid flow of air on the other side, so that the two metal surfaces are 90°C and 20°C, respectively. How many joules are conducted through the plate per minute? [Note that for steel, k = 0.15 J-cm/cm2-s-°C]
A. 1755 B. 1575 C. 1557 D. 1775
B. 1575
MAY 2022. The true density of a concrete to which an air- entraining agent was added is 2.80 g/cm3. However, a dry core (15.24 cm x 10.16 cm in diameter) of this concrete weighs only 2.982 kg. The same core weighs 3.08 kg when saturated with water. What are the percents of the open and closed pores?
A. open pores = 7.9% and closed pores = 7.9%
B. open pores = 5.9% and closed pores = 5.9%
C. open pores = 7.9% and closed pores = 5.9%
D. open pores = 5.9% and closed pores = 7.9%
C. open pores = 7.9% and closed pores = 5.9%
The true density of a concrete to which an air-entraining agent was added is 2.80 g/cm3. However, a dry core (15.24 cm x 10.16 cm in diameter) of this concrete weighs only 2.982 kg. The same core weighs 3.08 kg when saturated with water. What are the bulk and apparent densities?
A. bulk density = 2.14 and apparent density = 2.26
B. bulk density = 2.62 and apparent density = 2.41
C. bulk density = 2.41 and apparent density = 2.62
D. bulk density = 2.26 and apparent density = 2.14
C. bulk density = 2.41 and apparent density = 2.62
NOV2021.Aconcreteunitmixcontains136kgofgravel,95 kg of sand, 42.5 kg of portland cement, and 22.5 kg of water, plus 5% entrained air. How much cement is required to build a low retaining wall, 28.6 cm x 1.07 m x 0.305 m? The aggregate is nonporous.
Material TRUE BULK
Gravel 2.6. 1.76
Sand 2.65. 1.68
Cement. 3.25 1.5
A. 71.1 unit mixes
B. 75.1 unit mixes
C. 71.5 unit mixes
D. 75.5 unit mixes
C. 71.5 unit mixes
Anelectricalporcelainproducthasonly1%porosityassold.It has 27% porosity after pressing and drying, but before sintering. How much linear shrinkage occurred during sintering?
A. 9.9%
B. 7.9%
C. 7.7%
D. 9.7%
9.7%
