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C11.1 Density AQA AS Physics P11 Materials Kerboodle Answers: Page No. 185
1.Ans-
a its volume,
8.0 x 10-4 m3
b its density.
3.1 x 103 kgm-3
2.ANS-
a the mass,
6.3kg
b the volume,
2.0x 10-3 m3
c the density of the paint in the tin.
3.1×103 kgm-3
3.Ans-
a its volume in rn3,
9.6 x 10-6 m3
b its mass in kg. The density of steel = 7800 kg m-3
7.5 x 10-2 kg
4.Ans-
a the mass of
i aluminium,
0.29kg
ii magnesium in the tube,
0.12kg
b the density of the alloy. The density of aluminium = 2700 kg m-3
The density of magnesium = 1700 kg m-3
2.3 x 103 kg m-3
11.2 Springs AQA AS Physics P11 Materials Kerboodle Answers: Page No. 188
1.
a the extension of the spring when the tension in it is equal to ION
0.40m
b the tension in the spring when it is extended by 0.50m from its unstretched length.
12.5N
2.a the tension in each spring
20N
b the extension of each spring
100mm
c the spring constant of each spring.
200Nm-1
3.a
40N
b for the two springs in series and vertical.
200mm
4.a the spring constant
12.3Nm-1
b the energy stored in the spring
8.8 x 10-2 J
c the weight that needs to be added to extend the spring to 600 mm.
2.2 N
11.3 Deformation of solids AQA AS Physics P11 Materials Kerboodle Answers: Page No. 191
1.1.0 x 109 Pa
2.
1.3 x 1011 Pa
3.a the tensile stress in the wire
9.4 x 108 Pa
b the extension of the wire.
The Young modulus of steel 2.1 x 1011 Pa.
1.1 x 10-2m
11.4 More about stress and strain AQA AS Physics P11 Materials Kerboodle Answers : Page No. 193
1.a the tensile stress in the cable,
3.3 x 106 Pa
b the extension of the cable,
2.8 x 10-4 m
c the elastic energy stored in the cable, assuming its elastic limit has not been reached.
0.21 J
2.
2.3mm
b the elastic energy stored in the wire.
1.7 x 10-2 J
3.
a the compressive force exerted on the bar,
470kN
b the work done to Compress it.
47J
4.
a the work done to stretch the rubber band to an extension of 0.40 m,
10.0J
b the internal energy retained by the rubber band when it unstretched.
4.2J
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Practice questions: Page No. 194-195
1. (a) The density of a material is the mass per unit volume
(b) Density of copper 8.9 x 103 kg m-3
Density of zinc 7.1 x 103 kg m-3
(i)
Volume of copper = 0.70 × 0.80 × 10-3
= 0.56 × 10-3 m3
Mass of copper
= ρCVC = 8.9 × 103 × 0.56 × 10-3
= 5.0 kg
Mass of zinc
= ρZVZ = 7.1 × 103 × 0.30 × 0.80 × 10-3
= 1.7 kg
(ii)
Force applied to spring = weight of lorry = mg
= 1.2 × 103 × 9.81 = 1.18 × 104 N
3 (a)
(i)
Material X obeys Hooke’s law until it fractures because stress is proportional to strain over the whole line
(ii) is the weaker material
Y is the weaker material because its breaking stress is lower than that of X
(iii) is ductile
material Y is ductile because it exhibits plastic behaviour
(iv) has the greater elastic strain energy for a given tensile stress (8 marks)
Material Y has the greater strain energy for a given tensile stress because the area under its graph is greater for a given tensile stress
(b)
(i) cross-sectional area = 0.64 mm2
= 0.64 × 10−6 m2
(ii)Energy stored in cord
4.
(a)Graph plotted to include:
• At least 9 points plotted correctly
• All 12 points plotted correctly
• correct graph for increasing loads, linear up to about 80 N and with curved part for higher loads >80 N
• Correct linear graph for decreasing loads, with permanent extension for zero load
(b).Relevant points include:
• Initially the wire obeys Hooke’s law (or behaves elastically)
• This continues up to the limit of proportionality
• The elastic limit is reached beyond the limit of proportionality
• The wire then undergoes plastic deformation
• Which produces a permanent extension
• Extension varies linearly with load as the load is decreased
(c).
5.
(i)
(ii)
(iii) The cross-seasonal area 01 each wire is I .4 x 10*’ and the unstretched length is 1.5 m. Determine the extension produced in either wire. (3 marks) AQA, 2005
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