Intermediate physics / by W. Watson.

  • Watson, W. (William), 1868-1919.
Date:
1912
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Licence: In copyright

Credit: Intermediate physics / by W. Watson. Source: Wellcome Collection.

Provider: This material has been provided by UCL Library Services. The original may be consulted at UCL (University College London)

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    CHAPTER V 1. Give an account of an accurate method of determining /. A gram of coal in burning gives out 8000 calories. With what velocity- must a mass of coal be moving to contain the same amount of mechanical energy as it would give out in burning ? 2. With what velocity must a lead bullet strike a target in order that its tempera- ture may rise 100°, supposing half the heat due to the impact to be retained by the bullet ? (Specific heat of lead = 0-03.) 3. A paddle turns about a vertical axis in a calorimeter which contains water and is pivoted so that it can turn about a vertical axis. If a couple of lO'' dynes- cm. has to l)e applied to prevent its rotation, calculate the rise in temperature of the water while the paddle makes 1000 revolutions, if the water equivalent of the vessel and its contents is 2000. 4. Explain what is meant by the terms specific heat of a gas (1) at constant pressure and (2) at constant volume. ^ Explain carefully why one is greater than the other, and what assumptions would enable you to calculate the difference of these specific heats at any pressure if you were given the value of the mechanical equivalent. 5. Find an expression for the work done by a gas when expanding against a constant pressure. 6. Describe Joule and Kelvin's method for determining the work performed against molecular forces when a gas expands, and the way in which the eff'ect observed lias been applied to the liquefaction of air. 7. Explain what is meant by {a) an isothermal and (&) an adiabatic curve, and show how the work performed during an isothermal or adiabatic change in the case of a gas can be represented on the p-v diagram. 8. What is the critical point for a gas, and what is the general form of the isothermals for temperatures near the critical temperature ? 9. Find an expression for the adiabatic elasticity of a gas. 10. Describe the Carnot cycle, and find an expression for the efficiency of an engine working on this cycle between given temperature limits. 11. Show that the efficiency of an engine working between any two temperatures is a maximum if the cycle on which it works is reversible. 12. What is the efficiency of an engine working on a reversible cycle between the temperature limits 200° 0. and 0° C. ? 13. Explain how Kelvin's absolute scale of temperature is arrived at. 14. If a mass of saturated air is allowed suddenly to expand a cloud is formed. Explain this phenomenon. BOOK III CHAPTERS I AND n 1. Draw the harmonic curves for two S.H.Ms., the periodic time for one being 12 seconds and for the other 3 seconds, the amplitude of the first being 4 times that of the second. Also draw the curve which represents the result of adding these together, the phase at the start being the same when the displacements are zero. 2. A particle executes a S.H.M. Find expressions for the velocity and acceleration in terms of the amplitude, periodic time, and the displacement. 3. Explain what is meant by the phase of a S.H.M. Plot a curve showing the result of compounding two S.H.Ms, of equal period and amplitude in directions at right angles, the phases differing by 90° or a quarter period. 4. Find the resultant of two S.H.Ms, in the same direction and having the same period, the phase of one being 90° ahead of the other; the amplitude of the more advanced being twice that of the other. 5. Find an expression for the period of a simple pendulum. 6. Explain what is meant by simple harmonic motion. If a particle moves back- wards and forwards through a distance of 20 cm. five times a second with a S.H.M., find its greatest velocity and its greatest acceleration. 7. Find an expression for the velocity with which the bob of a simple pendulum