Cork Institute of Technology
Bachelor of Engineering (Honours) in Structural Engineering – Stage 1
(NFQ – Level 8)
Autumn 2007
PHYSICS
(Time: 3 Hours)
Answer FIVE questions only.
Show ALL working to gain full marks.
Assume: g = 10.0 ms-2
Examiners: Mr. P. Anthony
Prof. P. O Donoghue
Dr. M.E. Woods
Q1. (a) State THREE assumptions of the Kinetic Theory of Gases. (3 marks)
(b) (i) State Charles' Law.
(ii) Explain how a graphical plot of measurements taken to verify Charles' Law for an
ideal gas leads to the concept of an Absolute Temperature Scale and Absolute Zero
Temperature. What is the unit of the Absolute Temperature Scale? (6 marks)
(c) An air bubble at the bottom of a lake 50 m deep has a volume of 1.00 cm3. The
temperature at the bottom is 7 oC and the surface is at 27 oC. [Atmospheric pressure is 1.00
x 105 Pa and the density of water is 1000 kg m-3.]
(i) Calculate the total pressure at a depth of 50 m in the lake.
(ii) Determine the volume of the bubble just as it reaches the surface. (11 marks)
Q2 (a) A copper cable of length 1.0 km and circular cross-section, has a resistance of 30 Ω. The
resistivity of copper is 1.7 x 10-8 Ω m. What is the radius of the wire? (6 marks)
(b) A d.c. battery of emf 12.0 V is connected across three resistors R1, R2 and R3 connected in
parallel: R1 = 5 Ω, R2 = 10 Ω, R3 = 30 Ω.
Determine:
(i) the equivalent resistance [Re] of the three resistors;
(ii) the power dissipated in R1.
(iii) the total circuit current I.
(iv) The heat energy emitted by R2 in 20 seconds. (14 marks)
