CN1182496C - Experimental instrument for demonstrating bowl on guide rail - Google Patents

Abstract

The present invention relates to a demonstration experiment instrument of a guide rail rolling ball, which belongs to the field of a teaching experiment instrument. The experiment instrument is composed of a base plate, guide rails, starters and a rolling ball, wherein the base plate is provided with two sets of guide rails; each set of the guide rails are composed of two arc plates; the length, the height and the arc of the four arc plates are completely identical; the two sets of the guide rails are composed of the four arc plates; each two arc plates of each set of the guide rails are both vertically and parallelly fixed on the base plate, and has a certain distance; the distances of the two sets of the guide rails are different; one end of each guide rail is provided with the starter which can block the rolling ball and can release the rolling ball; the rolling ball is a ball-shaped rigid body. The experiment instrument can obviously demonstrate different movement speed of identical ball-shaped rigid bodies with different rotation radiuses.

Description

Guide rail spin demonstration test instrument

Technical field

The present invention relates to guide rail spin demonstration test instrument, belong to College Physics lecture experiment instrument field.

Background technology: the lecture experiment that the rotational symmetry rigid body rolls along the inclined-plane, significant to the rule of the plane parallel motion that helps university student's correct understanding rigid body.Once there was bicylindrical in the domestic colleges and universities that have along the lecture experiment that rolls the contrast speed under the straight inclined-plane, but because the length on straight inclined-plane can not be oversize, and it is not obvious to roll speed difference under two cylinders, is difficult to differentiate with estimating.So experimental demonstration poor effect.

Summary of the invention

Center of mass theorem explanation in the College Physics, the acceleration of rigid body or system of particles barycenter equals bonding force divided by gross mass; The characteristics of center-of-mass angle are that inertial force system is zero for arbitrary moment by barycenter, so handle the rotational problems of rigid body in center-of-mass angle, can be inertial system as need not manage it in inertial system; The kinetic energy of Ke Nixi theorem explanation rigid body equals the kinetic energy of barycenter and the kinetic energy sum of the axle rotation that rigid body is walked around barycenter.Can find the solution the problem of rotational symmetry rigid body in view of the above along the dip plane plane parallel motion.As Fig. 1. shown in, the center-of-mass coordinate of rigid body represented with y.

Analyze the suffered power of rigid body O: gravity mg acts on barycenter straight down; Normal pressure N makes progress perpendicular to the inclined-plane, acts on end Side portion, and line of action of force is crossed barycenter; Stiction f makes progress along the inclined-plane, acts on end Side portion.It is as follows to list equation according to above-mentioned principle.

$\mathrm{mg}\sin a-f=m\stackrel{\·\·}{y}.$

N-mg?cos?α＝0

$\mathrm{fR}=J\stackrel{\·\·}{\mathrm{\θ}}$

$\stackrel{\·\·}{y}.=R\stackrel{\·\·}{\mathrm{\θ}}$

In the formula, R is the radius of gyration of rigid body, and J is the moment of inertia of rigid body.Can solve following result in view of the above.These results tell us m, J, R equivalent are how to influence movement of Rigid Body, for example following second formula tell we at m, when J is identical, the acceleration of rigid body barycenter increases with the increase of R.Two rolling rigid bodies that this instrument is chosen are two even spheroids, and their radius r is identical, and quality m is identical, moment of inertia J (=0.4mr ²) also identical, but their radius of gyration R difference.Thereby the difference of two ball rolling movement speeds can reflect the influence of radius of gyration R.

$\stackrel{\·\·}{\mathrm{\θ}}=\frac{\mathrm{mgR}\sin a}{J+m{R}^2}$

$\stackrel{\·\·}{y}=\frac{{\mathrm{mgR}}^2\sin a}{J+{\mathrm{mR}}^2}$

$f=\frac{\mathrm{mgJ}\sin a}{J+m{R}^2}$

N＝mg?cos?α

The purpose of this invention is to provide the tangible guide rail spin of a kind of experiment effect simple in structure demonstration test instrument.

This instrument is made up of base plate, guide rail, starter and spin.Two groups of guide rails are set on base plate, and every group of guide rail is made up of two arcs.Length, height and the arc of four arcs that constitutes two groups of guide rails is identical.Two arcs that constitute every group of guide rail all vertically are fixed on the base plate, and two arcs are parallel to each other at regular intervals.The arc spacing difference of two groups of guide rails is so formed two groups of guide rails that width is different.Because two guide rail width differences, so it is inequality that identical spin is placed on when top its radius of gyration.End at guide rail is provided with starter.Starter can block spin and discharge spin.Spin is a spherical rigid body.

During experiment, earlier two spin are placed on an end of two guide rails respectively, and block with starter.Pressing starter release spin during the experiment beginning makes them with rolling at present.Petahque promptly returns behind the other end of guide rail automatically.Motion repeatedly because run duration is longer, is accumulated small movement differential and so forth, just can allow the people find out that very intuitively which is faster.This instrument can clearly be demonstrated the difference of the identical spherical movement of Rigid Body speed of the different radiuses of gyration.Continue observation, see which ball stops earlier, can help people to understand the influence of the radius of gyration the spin energy consumption.

Description of drawings:

Fig. 1. be the STUDY ON PLANE PARALLEL MOTION OF RIGID BODY principle schematic;

Fig. 2. be this demonstration test instrument schematic side view;

Fig. 3. be Fig. 2. vertical view;

Fig. 4. be the arc plate structure synoptic diagram.

Embodiment:

This demonstration test instrument (see Fig. 2., Fig. 3 .) by base plate 1, wide guide rail 2, narrow guide 3, decorative panel 4, compositions such as starter 5 and spin 6.Every group of guide rail is made up of two arcs 7, and guide rail arc 7 links to each other with decorative panel 4, is fixed on the base plate 1.The arc spacing difference of two groups of guide rails, thus two groups of guide rails that width is different formed.Because guide rail width difference, so spin is placed on its radius of gyration difference when top.Starter 5 is installed on the decorative panel 4, can rotate around stationary shaft, can block or discharge spin to reach.The radius-of-curvature of arc 7 is 530-600mm; The high about 200mm of straight flange; Thickness of slab 3-5mm.The arc spacing of wide guide rail is 40-42mm; The arc spacing of narrow guide is 24-30mm.Ball diameters is Φ 50-52mm.

Claims (1)

1, a kind of guide rail spin demonstration test instrument, it is characterized in that: form by base plate, guide rail, starter and spin, two groups of guide rails are set on base plate, every group of guide rail is made up of two arcs, length, height and the arc of four arcs that constitutes two groups of guide rails is identical, two arcs that constitute every group of guide rail all vertically are fixed on the base plate, two arcs are parallel to each other at regular intervals, the arc spacing difference of two groups of guide rails, end at guide rail is provided with starter, starter can block spin and discharge spin, and spin is a spherical rigid body.

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