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- 1. Multiple Choice
The table contains information on four wires. It shows the stiffness of each wire and the maximum strain energy stored in the wire when extended to the breaking point.
Assume each wire has the same initial dimensions and obeys Hooke’s law.
Which wire extends the least before reaching the breaking point?
A
B
C
D
- 2. Multiple Choice
A non-uniform sign is 0.80 m long and has a weight of 18 N
It is suspended from two vertical springs P and Q. The springs obey Hooke’s law and the spring constant of each spring is 240 N m–1
The top end of spring P is fixed and the top end of spring Q is adjusted until the sign is horizontal and in equilibrium.
What is the extension of spring Q?
0.014 m
0.038 m
0.049 m
0.061 m
- 3. Multiple Choice
What is the name given to a material that breaks without deformation when a force is applied to it?
Plastic
Brittle
Stiff
Elastic
- 4. Multiple Choice
Two separate wires X and Y have the same original length and cross-sectional area.
The graph shows the extension ∆L produced in X and Y when the tensile force F applied to the wires is increased up to the point where they break.
Which statement is incorrect?
For a given extension more energy is stored in X than in Y.
The Young modulus of the material of wire Y is greater than that of wire X.
Both wire X and wire Y obey Hooke’s law.
Wire X has a greater breaking stress than wire Y.
- 5. Multiple Choice
A load of 3.0 N is attached to a spring of negligible mass and spring constant 15 N m–1.
What is the energy stored in the spring?
0.3 J
0.6 J
0.9 J
1.2 J
- 6. Multiple Choice
The diagram shows how the stress varies with strain for metal specimens X and Y which are different. Both specimens were stretched until they broke.
Which of the following is incorrect?
X is stiffer than Y
X has a higher value of the Young modulus
X is more brittle than Y
Y has a lower maximum tensile stress than X
- 7. Multiple Choice
Two vertical copper wires X and Y of equal length are joined as shown. Y has a greater diameter than X. A weight W is hung from the lower end of Y.
Which of the following is correct?
The strain in X is the same as that in Y.
The stress in Y is greater than that in X.
The tension in Y is the same as that in X.
The elastic energy stored in X is less than that stored in Y.
- 8. Multiple Choice
Two masses hang at rest from a spring, as shown in the diagram. The string separating the masses is burned through.
Which of the following gives the accelerations of the two masses as the string breaks?
acceleration of free fall = g
A
B
C
D
- 9. Multiple Choice
The overhead cables used to transmit electrical power by the National Grid usually consist of a central core of steel cables surrounded by a sheath of cables of low resistivity material, such as aluminium.
What is the main purpose of the steel core?
To force more current into the outer sheath.
To provide additional current paths through the cables.
To reduce the power lost from the cables.
To increase the mechanical strength of the cables.
- 10. Multiple Choice
The four bars A, B, C and D have diameters, lengths and loads as shown. They are all made of the same material.
Which bar has the greatest extension?
A
B
C
D
- 11. Multiple Choice
For which of the following relationships is the quantity y related to the quantity x by the relationship
A
B
C
D
- 12. Multiple Choice
A load of 4.0 N is suspended from a parallel two-spring system as shown in the diagram.
The spring constant of each spring is 20 N m–1. The elastic energy, in J, stored in the system is
0.1
0.2
0.4
0.8
- 13. Multiple Choice
The graph shows the variation of stress with strain for a ductile alloy when a specimen is slowly stretched to a maximum strain of εm and the stress is then slowly reduced to zero.
The shaded area
represents the work done per unit volume when stretching the specimen
represents the energy per unit volume recovered when the stress is removed
represents the energy per unit volume which cannot be recovered
has units of J m–1
- 14. Multiple Choice
The force on a sample of a material is gradually increased and then decreased. The graph of force against extension is shown in the diagram.
The increase in thermal energy in the sample is represented by area
R
P + Q
P + Q + R
P + Q − R
- 15. Multiple Choice
A stone is projected horizontally by a catapult consisting of two rubber cords. The cords, which obey Hooke’s law, are stretched and released. When each cord is extended by x, the stone is projected with a speed v. Assuming that all the strain energy in the rubber is transferred to the stone, what is the speed of the stone when each cord is extended by 2x?
v
2v
4v
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