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The Stone Impact Experiment
Link between Magnetism and Inertia:
There is a link between the magnetism and inertia. An accelerating object generates magnetic field inside and nearby the object and this magnetic field is responsible for inertia. A new experiment was conducted to validate the same.
Keyword : dj / dt
Introduction:
By definition, Inertia is the property of matter because of which it
continues to be in rest unless a force acts on it or continues to be in motion
unless a force acts on it.
The major forces in nature are Electric, Magnetic, Inertial and Gravitational which are applicable at larger distances. Among these forces, the link between Electricity and Magnetism are well known, but there is no established link of electricity or magnetism with Inertia. It is assumed that Magnetism and Inertia are closely linked. Whenever an object is accelerated, it generates rate of change of magnetic flux dj / dt which in turn generates eddy-current damping at atomic scale. This eddy current damping opposes the dj / dt
and the object experiences a drag. This is Inertia. Effect of this magnetic
field can be observed near the accelerating / decelerating object which is
validated by "Stone Impact Experiment" described in section II.
Experiment:
Equipment/ Items Used
- Tektronix TDS 210 Digital Scope
An AC Amplifier used for tests conducted on May 28 and 29, 2001 to check existence of pulse generated in the coil. A better DC amplifier was used for tests conducted on June 4 and 5, 2001.
Ordinary Laser pointer as light source facing the optical sensor/ Photo Transistor connected to Channel 1 of the Scope
Stones of average diameter 81 mm and mass 820 grams approximately ( multiple stones were used )
Plastic pipe of inner diameter 133 mm to guide the stone
Coil : SWG 30, 1000 Turns, 200 mm diameter
The following experiment is named as "Stone Impact Experiment" which validates the link between Magnetism and Inertia. The Impact generates very high acceleration / deceleration for a short duration. Therefore an impact of free falling stone on a wooden cylindrical core generates sufficiently high acceleration pulse which subsequently generates rate of change of magnetic flux dj / dt. This can be captured by a coil surrounded the wooden core.
Setup:
A hard plastic pipe 9.45 metres (31 feet) long was mounted well with supports as shown in Fig 3.1. The pipe ended just around a feet above the wooden core approximately. A coil connected via an amplifier to the second channel of a 2 channel Digital Scope. This coil is placed on a sponge disc on the ground to isolate vibrations. This coil has a larger diameter than the pipe to provide sufficient clearance during the stone impact. A wooden cylinder is placed at the center of the coil which acts as an anvil so that the stone impacts upon the wood.
An optical sensor is connected to Channel 1 of the Digital Scope. The sensor is placed above the coil to deliver a Synchronizing pulse (SYNC) for the scope.
A stone is dropped from the top of the pipe. The stone has a smaller diameter than the pipe so that it does not interfere or drag against the inner walls of the pipe. Before striking the wooden anvil, the stone first crosses the optical sensor giving SYNC and then impacts the anvil within the coil area. The impact of the stone generates high retardation and a signal is induced in the coil.
The experiment has been conducted to validate whether the induced signal is related to the impact or is the induced signal zero. If the signal is not zero, this indicates that an EMF has been induced in the coil by applying high acceleration/ retardation of an object (stone).
It was observed that an EMF has been induced in the coil and the induced signal has been displayed on the Channel 2 of the Scope.
Observations on May 29, 2001:
Each picture shows the SYNC pulse from the Optical Sensor when the stone passes it and a signal on Channel 2 after striking the anvil within the coil. In first case, the wooden anvil was placed on a rubber disc.
In another case, the rubber disc was removed and still the results were similar i.e. the induced signal was observed.
Observations on June 4, 2001:
T he distance
between the sensor and the anvil was reduced.
 
Observations on June 5, 2001:
This particular stone related to Fig 3.6 had some permanent magnetism.
The large size pulse is generated due to flux linkage between the stone and coil.
Note: The noise seen in Channel 2 induced signal is from the 50 Hz mains
Inferences:
Velocity just before impact
v2 = u2 + 2gh
u = 0 (nearly)
g = 9.8 m/s2
h = 32’ 3" = 9.75 m + 0.0762 m = 9.83 m
v = 13.88 m/s
It is found that the Channel 2 signal seen on the scope is average 4V peak and having a pulse duration of 1 ms average. Thus dt = 0.5 ms. The amplifier before the scope has a gain of 100. The input signal to the amplifier that is coming from the coil is 4/ 100 = 0.04 V = 40 mV peak.
Estimating
f and df /dt generated due to stone impact by comparison method:
The same coil was used now referred to as secondary coil (Secondary Coil L2). In the inner empty space of the coil another coil was placed which is referred to as Primary Coil (Primary Coil L1) which has 8.5 cm diameter which is close to the value of the stone diameter.
The Primary Coil L1 is placed within the Secondary Coil L2 as shown in Fig 3.9 with a suitable current limiting resistor in series with the Primary Coil L1 and excited by DC current of 333 mA.
The magnetic flux density measured on Primary Coil L1, axially, was found to 6.5 Gauss approximately.
Thereafter, a half Sine Pulse was fed to Primary Coil L1 and similar pulse was induced in Secondary Coil L2 ( similar to that after the stone impact). The current measured in the Primary Coil L1 was 3 mA approx. to induce similar pulse.
The upper trace in Figures 3.10 and 3.11 shows the input to the Primary Coil L1 and the lower trace shows the signal induced in the Secondary Coil L2.
It is measured that the current pulse of 3 mA induces signal in the Secondary Coil L2 similar to the signal generated by stone impact.
Proportionately, for 3 mA, the magnetic flux density in L1 would be
B = 6.5 * (3/ 333) = 0.059 gauss
A = Area of Primary Coil L1 = p *r*r where r is the radius of L1
r = 8.5 / 2 = 4.25 cm = 0.0425 m
A = 0.0057 sq. m
j = A*B Wb
= 0.0057 * 0.059
= 0.000336 Wb
d j / dt = 0.000336 Wb / 0.5 ms (An impact will generate a similar duration pulse, generally)
= 0. 672 Wb/s
is the rate of change of flux which is brought about by the sudden deceleration of the stone (inertia) which causes voltage to be induced in the Secondary Coil L2.
To get an idea of the deceleration value:
As calculated above, the velocity just before the impact is 13.88 m/s. This is suddenly reduced to zero due to the impact in approx. 500 us.
As per Newton’s law of motion:
v = u + at
0 = 13.88 + a(0.5 * 10-3)
a = #9; 27760 m/s2
= #9; 2832 g
Thus 2832 g deceleration generates a flux of the order of 0.000336 Wb and the rate of change of flux is of the order of 0. 672 Wb/s.
Conclusion:
When the stone impacts the wooden anvil, there is a voltage pulse induced in the coil. The impact of the stone is nothing but sudden deceleration (Inertia). The stone impact causes rate of change of magnetic flux, which induces the voltage pulse in the coil. This establishes a link between magnetism and inertia.
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