A question 100 for the determination of gravitational constants

In fact, this device also calculates friction, which provides a counterclockwise drag moment, which is balanced with the clockwise kinetic moment generated by the gravitational force provided by the gravitational field formed by the large sphere, and then forms a state as shown in the figure.

Remember that there is a spring on the plane mirror of this device, you said f=k is the elastic force is right, the original expression of elastic force f=kx, but, because lim(sinx x) = 1 [x 0], and the deflection angle is very small, the rotation radius of the spring is assumed to be 1, [this can be done through experiments, then the distance of the spring rotation is 1 sin, of course, there is also an approximation here, that is, when the angle is very small, the limit of the length of the turned chord and the length of the arc is equal. That's why there's the expression f=k.

Also for a separate ball analysis, f provides the drag moment, gravitational force is the kinetic moment, and f=k =gmm'r. Speaking of this, it is equivalent to explaining the question that follows you. and g=k r mm'.

k is the stiffness coefficient of the spring [(also known as the stubbornness coefficient. If the radius of rotation of the spring is not 1, but any constant c, then this k can be seen as the product of the spring stiffness coefficient k' and c, which means that the two constants are treated as one coefficient. ], and r, as well as m, m' can all be obtained by direct measurement.

It is worth noting that the angle of laser deflection is twice the angle of spring deflection, that is, =2, which is related to the rotation of the plane mirror, you can draw a diagram yourself, the angle between the incident ray and the refracted ray is bisected by the normal of the plane mirror, and the angle at which the plane mirror turns is the angle between the incident ray and the normal of the plane mirror.

Why not 2f=gmm'What about r 2?

The plane mirror turns a, and the power of laser deflection is 2a!

In a nutshell:

The laser is reflected by the mirror, and the magnification and deflection angle when the mirror rotates is twice the actual one. Therefore, although there are 2 large and small balls that produce gravity, 2 to 2 does not pull!

Personal understanding: Actually, this is a logical problem, 2f=gmm'/r^2

f=ka=gmm'r 2 is OK, according to the representation on the diagram should be 2f

But why do we have multiple known constants as a formula?"2"This? The snake is enough; No matter how many known constants you use in your derivation, we can get into g.

And what laser deflected 2a so flattened the stream, you didn't look at the derivation carefully, how do you know that this formula was derived without considering this, so it seems that the speed will be calculated differently when calculating the speed in seconds and minutes.

In this experiment, one ball can be established in theory, but two balls are used for balance. I don't think a ball will be f=2gmm'r 2 bar! Even if it does, it will be converted to f=gmm'r 2, but this g = twice the gAbove.

Just memorize the formula, you don't know the specific situation of the test!

It is the two forces that deflect the plane mirror, but the angle of the plane mirror deflection is half the angle of the laser beam deflection, 2f=k*(2a), which gives f=ka, according to gravitational force, f=gmm'/r^2=ka

So g = ka r 2 mm'。

This experiment is too classic.

Here f=ka is the given condition, and the gravitational formula is f=ka=gmm'r 2, so g = ka r 2 mm'。

As for the two F's you asked about providing the rotation of the plane mirror, it is true, assuming that the distance between the two spheres m and the midpoint of the two is l, then the rotation of the plane mirror is 2fl, but here f is the gravitational force between the two. The landlord took a closer look at the title. I thought about it......

The gravitational constant was measured by Cavendi.

The gravitational constant is.

Newton. The law of gravitation was discovered.

But what is the value of the gravitational constant g, even he himself does not know.

It is said that as long as the mass of two objects is measured, the distance between two objects is measured, and the gravitational force between objects is measured, and the law of gravitation is substituted, this constant can be measured. However, because the mass of ordinary objects is too small, the gravitational force between them cannot be measured, and the mass of celestial bodies is too large to measure the mass.

Therefore, the law of gravitation has been discovered for more than 100 years, and there is still no accurate result of the gravitation constant, and this formula still cannot be a perfect equation.

Until more than 100 years later, the Englishman Cavendish .

Using a torsion scale, this constant was cleverly measured. Its experiment in determining the gravitational constant is also known as the experiment of measuring the weight of the earth.

The gravitational constant, a term used in physics, is a physical term, and the accepted result is that the Cavendish determination of the g value is, and the latest recommended standard is g =. Usually take g =, if the centimeter gram second system is used, g = and its dimension is l·m·t.

The exact value of the gravitational constant g is calculated as follows: g = rv m, where m is the mass of the parent star, v is the linear velocity of the planet or moon, and r is the orbital radius of the planet or moon. Newton discovered the law of gravitation, but even he did not know what the value of the gravitational constant g was.

It is said that as long as the mass of two objects is measured, the distance between the two objects is measured, and the gravitational force between the objects is measured, and the law of gravitation is substituted, this constant can be measured.

However, because the mass of ordinary objects is too small to be measured, the gravitational force between them cannot be measured, and the mass of celestial bodies is too large to measure the mass. Therefore, the law of gravitation has been closed for more than 100 years, and the gravitational constant still does not have an accurate result, and this formula still cannot be a perfect equation. It wasn't until more than 100 years later that the Englishman Cavendish used a torsion scale to cleverly measure this constant.

The scientist who discovered the law of gravitation was Newton, who proposed the law of gravitational impact

The scientist who first measured the gravitational constant with relative accuracy was Cavendish, and after Newton obtained the law of gravitation, he did not measure the gravitational constant, which was measured by Cavendish using a torsion scale experiment

Therefore, d

Hello, the gravitational constant is measured by Cavendish with a torsion scale.

The main part of the torsion scale is a T-shaped light and sturdy frame that hangs upside down from a quartz wire. If two equal and opposite forces are applied to the ends of the T-frame, the quartz wire will be reversed by an angle. The greater the force, the greater the angle of torsion.

Conversely, if the angle at which the T-frame is turned can be measured, the force on both ends of the T-frame can also be measured. Now fix a small ball at each end of the T-frame, and then place a large ball near each ball, and the distance between the two balls can be easily determined. According to the law of gravitation, the large sphere will exert a gravitational force on the small ball, and the T-frame will twist with it, and the magnitude of the gravitational force can be measured as long as the angle of its torsion is measured.

Of course, since the gravitational force is small, the angle of this torsion will be small. How can this angle be measured? Cavendish installed a small mirror on the T-frame, and used a beam of light to shoot at the mirror, and the light reflected by the mirror hit the scale in the distance, and when the mirror and the T-frame made a small rotation, the spot on the scale would move greatly.

In this way, the effect of turning the small into the big is achieved, and the angle of twisting of the T-frame before and after placing the large ball is measured by measuring the movement of the spot, so as to determine the gravitational force of the large ball on the small ball at this time. Cavendish used this torsion scale to verify Newton's law of universal gravitation and to determine the value of the gravitational constant g. This value is very close to the value that has been measured by more scientific methods in modern times.

A. Kepler discovered the law of motion of the planets, so A is wrong B. Newton discovered the law of universal gravitation, but did not measure the gravitational constant g, it was Cavendish who measured g, so B is wrong

C. For the first time, Kaliang Kaiwendixu used a torsion scale experiment to measure the gravitational slag signal constant g, so C is correct

d. Classical mechanics based on Newtonian kinematics is only applicable to macroscopic and low-velocity objects, so D is wrong Therefore, C