# Tag Info

## New answers tagged definition

0

You do not need a unit for force when measuring inertial mass in Newtonian Mechanics. The only things you really need are the Newton's second law and the concepts of inertial frame and acceleration. The way you shall proceed is the following. Take a collection $\{m_i\}$ of (unknown) masses and a spring. Use the spring horizontally to accelerate the masses ...

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Let's look at: $$F_g=Gm_{g_1}m_{g_2}/r^2$$ For an object with mass $m_{g_1}$, on the surface of the earth, then: $$F_g=Gm_{g_1}M_E/R_E^2$$ Where $M_E$ is the mass of the Earth and $R_E$ the radius of the Earth. You can now verify that: $$GM_E/R_E^2=g=9.81\:\mathrm{m/s^2}$$ So we could have written the second expression as: $$F_g=m_{g_1}g$$ An object ...

-1

The distance covered by an object in particular direction is called Displacement

2

Short and a little inaccurate answer: vector is one-dimensional tensor, matrix is a two-dimensional tensor. More details now: Tensors are multidimensional arrays which have certain properties. Not every multidimensional array is a tensor, check this discussion for more details. There are two types of one-dimensional tensors: vectors and co-vectors. Both ...

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This may not be a definition of work. You need to put on more context. If the author was talking about how to get the work calculated, it is fair to make this statement.

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The definition of work: $$W=\int \vec F \cdot\mathrm{d}\vec x$$ So, work requires a force and a displacement. That is all. Think of it like this: If you push hard on a wall, you might use much effort to apply large force - but nothing moves and no work of use is done. If you push against a balloon, you can make it move very far. But you didn't really do ...

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A more general definition is ( the integral ) of force times distance. A static force, eg a body resting on a surface , does no work. The same body dropped has work done on it by the force caused by Gravity, potential energy being gradually converted to kinetic energy for the duration of the fall.

28

You're correct and the video is mistaken. In fact, if cesium atoms were constantly oscillating between the two hyperfine states, cesium beam clocks wouldn't work at all! In its simplest form, a cesium beam clock uses a magnet to separate a stream of atoms into two streams based on their hyperfine state; one state is selected to continue down the tube to be ...

8

Yes, they really are oscillating between two different states (not simply driven in one direction), but as you suspect they are not oscillating at the reference frequency. Rather than "just" sending radiation at the atoms to absorb, they also interact with an oscillating magnetic field (which is at the reference frequency). This field spurs some of the ...

32

The definition for the cesium clock is: 9192631770 cycles per second is frequency of the radio waves which cause maximum resonance, a physically measurable condition, in the cesium atoms. This corresponds to a particular tuning of the radio. Keeping it tuned provides the reference frequency cited.

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There is no fundamental difference between the two terms, except that in certain situations one or the other have come to be used more often. Gravity is more often used to describe the concept ("Newtonian Gravity"), the force (the "Force of Gravity"). Gravitation is more often used for phenomena resulting from gravity ("Gravitational Waves", "Gravitating ...

1

Gravity is the physical phenomena by which bodies attract themselves. It is the effect we observe. Gravitation is a model, a theory to explain the observed phenomena. The Newtonian Gravitation explains this phenomena in terms of attractive forces generated by massive bodies. It dos not depend whether the bodies are terrestrial or celestial. General ...

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For physical systems the external forces include 1. Applied Forces 2. Normal force of reaction 3. Force due to strings(tension) 4. Frictional forces between surfaces in contact Etc. Whereas internal force include 1.Force due to gravity between masses 2.Magnetic force between magnetic bodies 3.Electrical force 4 spring force etc. To identify ...

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You define a system which you are interested in. If there is no net external force acting on the system then linear momentum is conserved. You can identify internal forces as they must occur in equal in magnitude but opposite in direction pairs - Newton's third law. So you find a force in the system $\:\mathbf{f}_{12}\:$ which is the force on part $1$ of the ...

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The idea behind mechanical advantage is that the work put in equals the work you get out, but the force and distance can be different. So you get this equation: $$W_{in} = W_{out}$$ Then apply the definition of work: $$F_{in}d_{in} = F_{out}d_{out}$$ Solve for mechanical advantage, which is output ...

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Two dimensional CFTs separate into a left-moving sector and a right-moving sectors. The Virasoro generators $L_n$ act on the left-moving sector and ${\tilde L}_n$ act on the right-moving ones. Operators (or states due to the state-operator map) are labelled independently by representations of the left- and right-moving Virasoro. In particular, $h$ and ...

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UPDATED ANSWER : The centre of gravity will always be the same as the centre of mass in a uniform gravitational field (constant in magnitude and direction). This applies for bodies with non-uniform density as well as those with uniform density. The Earth's gravitational field can be considered uniform if the dimensions of the object are much smaller than ...

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The only condition for free fall as you said is that the motion of the body should be only under the influence of gravity alone. There should not be any effect of other forces like air resistance, viscous drag etc. The condition depends on the property of the material under free fall. For example, if the body has a certain mass as well as charged, it causes ...

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