Post Test Chapter 8 Deformation of Solids

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1.

Class: SMK (L) Methodist Kuala Lumpur STPM Physics Semester 1 Post Test Chapter 8 Deformation of Solids

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SECTION A A uniform, vertical wire is stretched by hanging a mass from its lower end. Which of the following does NOT affect the strain in the wire? A The Young Modulus of the wire B Its cross-sectional area C Its unstretched length D The load applied

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A mass of 2.0 kg is tied to the end of a steel wire which has an original length of 1.0 m, and the other end of the wire is fixed at point O. Later the mass is rotated about O in a vertical plane with constant angular speed of 4  rad s-1. If the cross-sectional area of the wire is assumed constant with a value of 1.0 mm 2, what is the minimum extension produced by the steel wire? [Young’s modulus of steel = 2.0 x 1011 Pa] A 0.40 mm B 0.50 mm C 1.48 mm D 1.58 mm

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Diagram 1 shows the strain of a wire varies when it is acted upon by a stress.

Diagram 1 The shaded region represents the A Strain in the wire B Stress on the wire C Strain energy stored in the wire D Strain energy per unit volume stored in the wire 4.

The force F required to extend a sample of rubber by a length x was found to vary as shown in Diagram 2.

Diagram 2 The energy stored in the rubber for an extension of 5 m was A more than 200 J B between 100 J and 200 J C 100 J D less than 100 J 5.

A wire has original length l, cross-sectional area A, force constant k, and Young’s modulus E. Find Young’s modulus E in the expression of k, A and l. A kA B Al C kl D A l k A kl

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The tensile stress in a uniform wire is the A length per unit extension B extension per unit length C cross-sectional area per unit force applied D force applied per unit cross-sectional area

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Two wires, P and Q are of the same length and diameter. The Young’s modulus for the material of P is twice that for the material of Q. The wires are stretched by loads of 3 kg and 2 kg.

The ratio of the extension of P to that of Q is A 1 B 4 5 5

C

5 4

D 5

8.

Two metal rods of the same Young’s modulus Y and the same cross-sectional area A, but of different lengths L and 2L respectively, are joined together end-to-end to form a rod of length 3L. What are the Young’s modulus and the force constant of the composite rod? Young’s modulus Force constant A 2Y 3 AY 2L B 2Y AY 3L C Y 3 AY L D Y AY 3L

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The stress-strain graphs for four types of materials are shown below.

The material that is most stiff is A P B Q 10.

C R

D S

When a metal wire is stretched over a limit, it undergoes plastic deformation. Which statement is true of plastic deformation? A Stress is proportional to strain. B The metal is not a crystalline solid. C The atomic planes slide over each other. D The atoms are displaced a little from their equilibrium position.

Section B 2/3

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A glass fibre of length 0.24 m and area of cross-section 8. 0 x 10-7 m2 is stretched until it breaks. The variation with load F of the extension x of the fibre is shown in the diagram below.

(a) (b)

State the reason whether glass is ductile, brittle or polymeric. [2 marks] Determine the Young’s modulus for the glass fibre. [3 marks]

2.

A cylindrical brass rod with Young’s modulus 9.7 x 1011 Pa and original diameter 10.0 mm experiences only elastic deformation when a tensile load of 200 N is applied. (a) Calculate the stress that produces the deformation. [3 marks] (b) If the original length of the rod is 0.25 m, calculate the change in the length of the rod. [2 marks]

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(a) (b) (c)

Define stress and strain for a stretched wire. [2 marks] Draw stress-strain graphs for a brittle material such as steel, a ductile material such as copper and a polymer such as rubber. [2 marks] A steel wire of length 2.5 m and cross-sectional 1.5 x 10 -6 m2 is fixed at one end. A load of 10 kg is hung from the free end so that the wire hangs vertically. The Young’s modulus of steel is 2.0 x 10 11 Pa. Calculate i. the stress applied. [2 marks] ii. the extension. [2 marks]

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