Page 178 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 13] ELASTICITY 163

Multiple-Choice Questions

13.1. The stress on a wire that supports a load depends on which one or more of the following?
(a) the wire’s length (c) acceleration of gravity
(b) the wire’s diameter (d) the mass of the load
13.2. A load causes a wire to stretch by the amount s. If the same load is applied to another wire of the same material but
twice as long and with twice the diameter, the second wire will stretch by the amount
(a) s/4 (c) s
(b) s/2 (d) 2s

13.3. At its elastic limit, the first wire of Question 13.2 could support a load of F. At its elastic limit, the second wire
could support a load of

(a) F/2 (c) 2F
(b) F (d) 4F

13.4. Young’s modulus for iron is 1.9 × 10 11 Pa. When an iron wire 1.0 m long with a cross-sectional area of 4.0 mm 2
supports a 100-kg load, the wire stretches by
(a) 0.0027 mm (c) 1.3 mm
(b) 0.27 mm (d) 3.7 mm

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13.5. Young’s modulus for brass is 1.3×10 lb/in. . When a brass rod 2 ft 4 in. long with a cross-sectional area of 0.50 in. 2
supports a 400-lb load, the rod stretches by
(a) 0.00015 in. (c) 0.0034 in.
(b) 0.0017 in. (d) 0.029 in.

13.6. Young’s modulus for aluminum is 7.0 × 10 10 Pa. When an aluminum wire 1.5 mm in diameter and 50 cm long is
stretched by 1.0 mm, the force applied to the wire is
(a) 247 N (c) 990 N
(b) 315 N (d) 2.42 kN
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13.7. The elastic limit of aluminum is 1.8 × 10 Pa. The maximum mass the wire in Question 13.6 can support without
going beyond its elastic limit is
(a) 32 kg (c) 623 kg
(b) 65 kg (d) 636 kg

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13.8. The ultimate strength of concrete is 2.0 × 10 Pa in compression. A concrete cube 80 cm on each edge can support
a maximum mass of
6
5
(a) 1.3 × 10 kg (c) 1.6 × 10 kg
7
6
(b) 1.3 × 10 kg (d) 1.3 × 10 kg
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13.9. The shear strength of a steel sheet 2.5 mm thick is 3.0 × 10 Pa. The force needed to punch a hole 6.0 mm square
in this sheet is
(a) 7.2 kN (c) 27 kN
(b) 18 kN (d) 18 MN
13.10. The bulk modulus of kerosene is 1.3 GPa. When a pressure of 1.8 MPa is applied to a liter of kerosene, its volume
decreases by
(a) 1.4 mL (b) 7.2 mL
(b) 2.3 mL (d)14 mL