2018年10月IB物理(SL)真题PDF下载-Paper3
1. In an investigation to measure the acceleration of free fall a rod is suspended horizontally by two vertical strings of equal length. The strings are a distance d apart.
When the rod is displaced by a small angle and then released, simple harmonic oscillations take place in a horizontal plane.
T=C/d√g
where c is a known numerical constant.
(a) State the unit of c.
(b) A student records the time for 20 oscillations of the rod. Explain how this procedure leads to a more precise measurement of the time for one oscillation T.
(c) In one experiment d was varied. The graph shows the plotted values of T against 1/d .
Error bars are negligibly small.
(i) Draw the line of best fit for these data.
(ii) Suggest whether the data are consistent with the theoretical prediction.
(d) The numerical value of the constant c in SI units is 1.67. Determine g , using the graph.
2. In an experiment to measure the specific latent heat of vaporization of water Lv , a student uses an electric heater to boil water. A mass m of water vaporizes during time t. Lv may be calculated using the relation
Lv=VIT/m
where V is the voltage applied to the heater and I the current through it.
(a) Outline why, during the experiment, V and I should be kept constant.
(b) Outline whether the value of Lv calculated in this experiment is expected to be larger or smaller than the actual value.
(c) A student suggests that to get a more accurate value of Lv the experiment should be performed twice using different heating rates. With voltage and current l1 V , I1 the mass of water that vaporized in time t is m1 . With voltage and current V2 , I2 the mass of water that vaporized in time t is m2 . The student now uses the expression
Lv=(V1I1-V2I2)t/M1-M2
to calculate Lv . Suggest, by reference to heat losses, why this is an improvement.
2018年10月IB物理(SL)真题余下省略！
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