A 6 m concrete slab of weight W is to be supported at one end by a steel rod 3 m long having a modulus of elasticity of 200000 MPa and the other end by an aluminum rod 4 m long with a modulus of elasticity of 70000 MPa. The lower ends of the rods are initially at the same level. 1. Which of the following gives the ratio of the area of the aluminum rod to that of the steel rod so that the slab will remain level after it is attached to the rods?
A 6 m concrete slab of weight W is to be supported at one end by a steel rod 3 m long having a modulus of elasticity of 200000 MPa and the other end by an aluminum rod 4 m long with a modulus of elasticity of 70000 MPa. The lower ends of the rods are initially at the same level.
1. Which of the following gives the ratio of the area of the aluminum rod to that of the steel rod so that the slab will remain level after it is attached to the rods?
a. 2.81
b. 3.81
c. 1.81
d. 4.81
2. Which of the following gives the elongation of the steel bar if it has a diameter of 25 mm when W = 30 kN.
a. 0.46mm
b. 0.66mm
c. 0.56mm
d. 0.76mm
3. Which of the following gives the strain of the aluminum rod?
a. 0.000215
b. 0.000315
c. 0.000115
d. 0.00445
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