US1559192A - Apparatus for demonstrating gravity acceleration - Google Patents

Description

D. G. SMYTH APPARATUS FOR- DEMONSTRATING GRAVITY ACCELERATION Filed April 6, 1925 2 Sheets-Sheet 1 n. a. SMYTH APPARATUS =FOR DEMONSTRATINGVEGRAVITY ACCELERATION 1 Gena-1,1925. 1559.192

Filed A ril 6, 1925 2 Shoots-SW9 2 Patented Got. 27 1925,

UNITED STATES DAVID e. sMYTH, or HARTFORD,.oonlvnorronrr.

' APPARATUS FOR DEMon'sTR TINe eRAvITY ACCELERATION.

' and useful Improvement in Apparatus for- Demonstrating Gravity; Acceleration, of which the following is a speoificatiom One of the .problems confronting the teacherof physics is theexperimental determination of the acceleration dueto gravity..

This invention relates to an apparatus for graphically illustrating a factor. of such problems.

' The object of the present invention is to provide a simple and inexpensive apparatus by means of which the distance traversed by a freely falling body in a known interval of time is registered mechanically with directness and accuracy upon a concrete object such a ribbon, tape, cord or the like.

In the accompanying drawings Fig. 1 is a perspective view of an apparatus that embodies the invention. Fig. 2 shows a recording strip which has been passedthrough the. apparatus and cut during a demonstration. Fig. 3 shows a difierent way of marking the strip. 4 shows a modified construction of the apparatus/ The structure illustrated has a vertical frame 1. supported by feetQ. In the first form, shown in Fig. 1, a curved or segmental ledge of metal 3 or other material is attached to the front face of the frame so as to extend outward therefrom. This ledge is Cal permanently fastened to the frame, as by lugs 4 and screw 5. In the second form, illustrated in Fig. 4, this ledgejis the peri'ineter of a wheel 6 rotarily mounted ona stud 7 j Extending downward from the top on the front face of the frame are a pair of ears 8 between which the upper end of a pendulum rod 9 is pivoted .the screw'10. The pendulum is sohung that-its planeof oscillation is parallel :to the face of the frame adjacent to ,the outel; edge of the ledge. A weight 11 is adjustable upon the pendulum rod, being held by a screw 12 in the position to which it is set. ,The lower end of the pendulum rodzma y be bent inward, as shown Application filed April 6, i925, Seriai No. 21,156.

in Fig. 1, and provided with a knife or pointed blade 13. The blade may be attached as shown in Fig. 1, so as to stand vertically with its cutting edge uppermost, or it may .be, as shown in Fig. 4:, in the shape *ofa knife with its cdgeset horizon-v t'ally. j In both cases the cutting edge or point of the blade is arranged so as to travel in a planeparallel with the plane of oscil lation of the pendulum. If desired, instead of a blade which will out or tear the strip, a pencil 14 or similar marking means may be attached to the pendulum, as illustrated in Fig. 3. a

vAn anvil block 15 preferably "of wood, is attached to the frame so that 'its face '16 is parallel with and adjacent to the vertical plane which is tangent to the ledge. I The block may be pivotally held by a. screw 17 so the block may be swung to one side, into a position where it will not interfere with the free oscillation of the pendulum, as shown by dotted lines in Fig.1. The face of this blockis desirably provided with an index mark, which may be a horizontal line 18. A stud 19 is set into the frameto form one limit for the oscillation of the pendulum. making use of this apparatus to determine the acceleration due to'gravity, the frequency of oscillation of the pendulum is ascertained by any of the well known methods, preferably by counting the number of oscillations ina known interval of time... A ribbonof paper 20, Fig. 1, or cord 21, Fig. 4, .or other light material, is laid around the band. One end of this flexible ribbon or cord is connected with the lower end of the pendulum rod. A. plummet 22 is attached to the other end of the. ribbonor cord below the anvil block. The mass of the plummet is sufficiently great to, acting through the ribbon or cord, retainthe pendulum. against the stop stud.' When this ribbon or cord .is severed adjacent to' the pendulum, as it may be by any suitable. means, the plummet drops and draws the a ribbon or cord overthe ledge and past the anvil block Coincidently the "pendulum.

swings away from the stoptoward the block until the point or edge of the knife blade reaches and piercesor severe the down-.

wardly drawn strip, or the pencil marks the strip. Before the connection between the ribbon and the pendulum is severed, however, it is necessary that a reference line 23 preferably horizontal be marked on the ribbon opposite the index line on the block or the cord be marked at the same point. The index line and the reference line are in the position which the point or blade of the knife or point of the pencilwou-ld strike the ribbon, when the pendulum is swung onehalf of an oscillation with the ribbon at rest. The distance from the reference line on the ribbon or cord to the point of puncture or severance of the ribbon or cord by' the blade is the distance through which the plummet has fallen during the interval. of one-half of'the oscillation of the pendulum. This distance and the factor of frequency of the pendulum are then used in the well known equation. (5 922) to give the answer to the problem, or the acceleration due to gravity.

By making use of a plummet the mass of which considerably exceeds the mass of the ribbon or cord errors due to the inertia of the ribbon or cord. or the friction against the ledge are reduced to a minimum. Should the ledge be rotatable, that is, formed on the rim of a wheel or pulley, the friction is.

still further reduced. The frequency of oscilla-tion of the pendulum may be varied by changing the position of the sliding weight. The function of the anvil block is to prevent the lateral motion of the ribbon or cord when intercepted by the blade, thus ensuring practically an instantaneous piercing of the ribbon orsevering of the cord.

The invention claimed is 1. A gravity acceleration apparatus comprising a frame, a ledge extending outward from the face of the frame, a pendulum supported by the frame and adapted to swing across its face, a plummet, a flexible strip loosely passing over the ledge and having one end connected with the plummet and the other end connected with the pendulum whereby the plummet through said strip temporarily holds the pendulum at one side of the center of its path of oscillation, and means carried by the pendulum and adapted to engage and mark said strip when the latter is severed and the plummet is allowed to drop and the pendulum allowed to swing.

2. A gravity acceleration apparatus. comprising a frame, a curved ledge extending outward from the face of the frame, a pendulum supported by the frame and adapted to swing across its face, a plummet, a flexible strip loosely passing over said ledge and having one end connected with the plummet and the other end connected with the pendulum whereby'the plummet through said strip temporarily holds the pendulum at one side. of the center of its path of oscillation,

and means carried by the pendulum and adapted to engage and mark said strip when the latter is severed and the plummet is allowed to drop and the pendulum allowed to swing.

3. A gravity acceleration apparatus comprising a frame, a ledge rotarily attached to the face of the frame, a pendulum supported by the frame and adapted to swing across its face, a plummet, a flexible strip loosely passing over said ledge and having one end' connected with the plummet and the other end connected with the pendulum whereby the plummet through said strip temporarily holds the pendulum at one side of the center of its path of oscillation, and means carried by the pendulum and adapted to engage and mark said strip when the latter is severed and the plummet is allowed to drop and the pendulum allowed to swing.

4. A gravity acceleration apparatus. comprising a frame, a ledge, extending outward from the face of the frame, a pendulum supported by the frame and adapted to swing across its face, a plummet, a flexible. strip loosely passing over the ledge and having one end connected with the plummet and the other end connected with the pendulum whereby the phunmet through said strip temporarily holds the pendulum at one side of the center of its path of oscillation. a marker carried by the pendulum and adapted to engage said strip when the latter is severed and the plummet is allowed to drop and the pendulum allowed to swing, and an anvil: block mounted on the frame in the path .of oscillation of said marker.

5. A gravity acceleration apparatus comprising a frame, a ledge extending outward from the face of the frame, a pendulum supported by the frame and adapted to swing across its face, a plummet, a flexible strip loosely passing over the ledge and having one end connected with the plummet and the other end connected with the pendulum whereby the plummet through said strip temporarily holds the pendulum at one side of the center of its path of oscillation, and a knife blade carried by the pendulum and adapted to engage said strip when the latter is severed and. the plummet is allowed to drop and the pendulum allowed to swing.

6. A gravity acceleration apparatus comprising a frame, a ledge extending outward from th face of the frame, a pendulum with an adjustable weight supported by the frame and adapted to swing across its face, a plummet, a flexible strip loosely passing over the ledge and having one end connected with the plummet and the other end connected with the pendulum whereby the plummet through said strip temporarily holds the pendulum at one side of the center of its path of oscillation, and means carried by the pendulum and, adapted to engage and mark said strip when the latter is severed connection between the plummet and penand the plummet is allowed to drop and the dulum, and means temporarily holding said pendulum allowed to swing. connection with its weighted end in the 10 7. A gravity acceleration apparatus compath of oscillation of the marker carried by 5 prising a frame, a pendulum supported by the pendulum.

the frame, a marker carried by and swinging with the pendulum, a plummet, a flexible I DAVI D G. SMYTH.

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