A simple experiment with a physical pendulum examining some aspects of rigid body motion is presented in this paper. The experiment consists of measuring the period of oscillation of a rod with non-homogeneous mass distribution used as a physical pendulum, dependent upon the position of the pivot axis. The obtained dependence provides sufficient information to calculate the position of the centre of mass, moment of inertia of the rigid body and local gravitational acceleration. This experiment is intended for secondary school and undergraduate students.

ABSTRACT:Broad line NMR and spin-lattice relaxation times T1 have been used to study glass transition phenomena in isotactic polypropylene modified and blended with an ethylene aminoalkylacrylate copolymer. By means of decomposition of spectra into elementary components corresponding to the chains with different mobility a softening due to the polymer modifier was observed. The modification results in an increase of fractions of amorphous and intermediate chains, respectively, gives rise to the enhancement of the chain mobility in amorphous regions, but the higher amount of the polymer modifier, which was used in the range up to I 5 wt%, the lower chain mobility in intermediate regions was found out. From the temperature dependences of the spin-lattice relaxation times T1 measured over the temperature range 290--430 K, a broadening of correlation time distribution on the side of the shorter correlation times has been found out to be and it was ascribed to overlapping of relaxation processes in amorphous regions. The sample containing the highest amount of the polymer modifier, in contrast to others, was shown to blend not only on the molecular level but also on the overmolecular.KEY WORDS In many of the previous works it was shown that isotactic polypropylene (PP) has a complex structure with regions of the different chain arrangement and different chain mobility. A heterogeneity, which may be studied by means of the broad line NMR spectra 1 -7 (ref I is to see the earlier papers) gives rise to the multiple transitions occuring in the temperature range around and above the glass transition ofPP. 8 Three components of the rotating frame spin-lattice relaxation times T 1 P with several relaxation minima in their temperature dependences also confirmed such relaxation behaviour. 9 · 10 On the other hand, due to spin diffusion only one relaxation time T1, a value of which is obviously determined by the most quickly relaxing, i.e., amorphous chains, may usually be measured. The minimum being appeared in the temperature range above the glass transition of PP corresponds to the f3 relaxation which was assigned to the glass transition phenomena. 9 · 11 -15In the precedent paper a considerable effect of the polymer modifier PFDA 522 on relaxation processes in PP was found out by the rotating frame spin-lattice relaxation times T 1P. 10 By the modification two temperature shifts towards the low temperatures were provoked in the amorphous regions of modified PP. They were the small shift only of the f3 relaxation corresponding to the segmental motion and the marked shift of the a. process, which was ascribed to the motion of the whole amorphous chains. This behaviour produced an overlapping of both discussed relaxations. It is reasonable to expect that this effect will also be observable by the spin-lattice relaxation times T1. But on the score of the spin diffusion only averaged parameters can be drawn from the T 1 measurements, an interpretation of which is not always unambiguos. On the other hand, it turns out that the b...

Three types of drawn PP fibres have been investigated by nuclear magnetic relaxation methods. The two minima observed in both the temperature dependence of T, and Tzeff are related to the well known pand a-processes, respectively.The results of the experiments show that in particular the crystalline regions are influenced by drawing. Kernmagmtische Relaxation in PolypropylenfasernMit Hilfe der kernmagnetischen Relaxation wurden drei Typen gereckter PP-Fasern untersucht. Die beiden Minima in den Temperaturabhangigkeiten von T, und Tzeff sind dem 8bzw. dem a-ProzeD zuzuordnen. Die Ergebnisse der Experimente zeigen, da5 durch die Reckung insbesondere die kristallinen Bereiche beeinfluJ3t werden. H3epnoaaztmmnaa penaxcay us e nonunponunenoebzx eonomax MeTOAOM RMP H3YYeHbI TPH THna RbITJTHYThIX ~OJIHnPOIlHJIeHOBbIX ROJIOKOH. ABa MHHHMYMa H a KpMBOfi 3aBHCA-MOCTII T I II Ea,#,@ OT TeMnepaTypM npnnncbmamcn npoqeccaM 8-H a-penaxcaqnu. IIonyseHHbIe p e~y n b~a~b~ no-Ka3bIBaH)T, YTO IIpOqeCC BbITIImKH OKa3bIBaeT BJIIIJTHUe o c o 6 e~~o H a KpHCTaJIJIH9eCKMe o 6 n a c~u .The influence of different preparation conditions upon formation of the morphological structure of polypropylene fibres was studied by X-ray method, scanning electron microscopy, and small-angle light scattering technique. It was found that the formation process and the deformation of the morphologic structure in polypropylene fibres changed when using the traditional and the high velocity technologies, respectively. Die morphologische Struktur von PolyprvpylenfasernDer EinfluS verschiedener Herstellungshedingungen auf die Bildung der morphologischen Struktur in Polypropylenfasern wurde mittels Rontgenbeugung, Scanning-Elektronenmikroskopie und Kleinwinkel-Lichtstreuung untersucht. Es wurde festgestellt, da8 der BildungsprozeB und die Deformation der morphologischen Struktur in den Polypropylenfasern sich beim Ubergang von der traditionellen zur Hochgeschwindigkeitstechnologie andern.

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A set of stretched isotactic polypropylene fibres prepared with the draw ratio λ = 2.5 at different temperatures was investigated by 1 H pulsed relaxation NMR method and continuous wave spectroscopy. Both, drawing and temperature of drawing influence physical properties of isotactic polypropylene fibres. NMR technique is shown to be advantageous for the study of these changes on molecular level since the shape of broad-line NMR spectra and processes of the NMR relaxation depend on the spatial configuration and motions of the resonating nuclei.