Faculty of Engineering
Engineering Physics 1BE (121)
Fall 2012
Dr Mohamed Fahmy
Sheet (3)
Temperature and thermal properties Part I
1. The concrete sections of a certain superhighway are designed to have a
length of 25 m. The sections are poured and cured at 10°C. Given that
the concrete average linear thermal expansion coefficient is
1210-6 C-1, What minimum spacing should the engineer leave
between the sections to eliminate buckling if the concrete is to reach a
temperature of 50°C?
2- At 20.0 oC a steel ball (𝛼 =1.10 ×10-5 oC-1) has a diameter of 0.900cm,
while a hole in an aluminum plate (𝛼 =2.20 ×10-5 oC-1) is 0.899cm. At
what temperature will the ball just pass through the hole?
3-A brass ring of diameter 10 cm at 20°C is heated and slipped over an
aluminum rod of diameter 10.01 cm at 20°C. Assuming the average
coefficients of linear expansion are constant (Brass=1910-6 C-1,
Al=2410-6 C-1), to what temperature must this combination be cooled
to separate them?
4- A 1.50-kg iron horseshoe initially at 600°C is dropped into a bucket
containing 20.0 kg of water at 25.0°C. What is the final temperature?
(Ignore the heat capacity of the container, and assume that a negligible
amount of water boils away.)
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Faculty of Engineering
Engineering Physics 1BE (121)
Fall 2012
Dr Mohamed Fahmy
5- A block of ice at 0 °C has a hollow in its top surface, as illustrated in
Fig. 5.1.
A mass of 160 g of water at 100 °C is poured into the hollow. The water
has specific heat capacity 4.20 kJ kg–1 K–1. Some of the ice melts and the
final mass of water in the hollow is 365 g.
(i) Assuming no heat gain from the atmosphere, calculate a value, in
kJ kg–1,for the specific latent heat of fusion of ice.
6. A 50 g copper calorimeter contains 250 g of water at 20 °C. How much
steam, initially at 100 °C, must be condensed into the water if the final
temperature of the system is to reach 50 °C? The specific heat of water is
4.19  103 J/kg °C, the specific heat of copper is 387 J/kg °C, and the
latent heat of the steam is 2.26  106 J/kg.
7. An aluminum cup of mass 200 g contains 800 g of water in thermal
equilibrium at 80.0°C. The combination of cup and water is cooled
uniformly so that the temperature decreases by 1.50°C per minute. At
what rate is energy being removed by heat? Express your answer in watts.
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Faculty of Engineering
Engineering Physics 1BE (121)
Fall 2012
Dr Mohamed Fahmy
Assignments
1. Some crushed ice at 0 °C is placed in a funnel together with an electric
heater, as shown in Fig.
The mass of water collected in the beaker in a measured interval of time is
determined with the heater switched off. The mass is then found with the
heater switched on. The energy supplied to the heater is also measured.
For both measurements of the mass, water is not collected until melting
occurs at a constant rate. The data shown in Fig. are obtained.
Calculate a value for the specific latent heat of fusion of ice.
2- A certain telescope forms an image of part of a cluster of stars on a square
silicon charge-coupled detector (CCD) chip 2.00 cm on each side. A star
field is focused on the CCD chip when it is first turned on and its
temperature is 20.0°C. The star field contains 5342 stars scattered
uniformly. To make the detector more sensitive, it is cooled to -100°C.
How many star images then fit onto the chip? The average coefficient of
linear expansion of silicon is 4.68 ×10-6 (°C)-1.
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