Quiz for the JUAS 2024 students – Special relativity | An online course about particle accelerators

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Quiz for JUAS students 2024 - Special Relativity

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1 / 20

Is it possible that a pure magnetic field seen by one observer in one reference system is transformed into an electric and magnetic field in another reference system?

No

Yes

2 / 20

What is the difference between nuclear power plants and particle accelerators?

None, both use E=mc2 to operate

Nuclear power plants use Uranium, Accelerators use hydrogen

In a nuclear power plant, mass is converted to energy, in an accelerator it is the opposite.

3 / 20

Will a moving object have a longer or shorter length (compared to its length at rest) for a stationary observer?

The same length

A longer length

A shorter length

4 / 20

What would be the energy of a proton accelerator in Fixed-Target mode to reach an energy of 100 TeV in the center of mass?

100 TeV * 15000

100 TeV * 213000

100 TeV

100 TeV * 100000

5 / 20

Which experiment led to the second postulate?

The Newton experiment

The Michelson-Morley experiment

The ATLAS experiment at the Large Hardon Collider

The Gallilée experiment

6 / 20

In the non-relativistic regime, what is the quantity that does not depend on the velocity of a charged particle moving in a constant magnetic field?

Its energy

The curvature of its trajectory

Its revolution period

Its velocity

7 / 20

With 4-vectors, the scalar product is defined and invariant under Lorentz transformations?

when taken between contravariant vectors only

when taken between covariant vectors only

when taken between covariant and contravariant vectors

8 / 20

What does 𝛽=0.5 mean?

𝛽=0.5 means that the object appears to be twice his length to a stationnary observer

𝛽=0.5 means that the object appears to be half of his length to a stationnary observer

𝛽=0.5 means that the object is moving at half of the speed of light

𝛽=0.5 means that it is a test version

9 / 20

What are the 2 relativistic Lorentz factors? (select all relevant answers)

Gamma: the Lorentz mass factor

Mu_0: the vacuum permeability

Beta: the ratio between the speed of the object and the speed of light

Alpha: the angle between the two arms of the Michelson-Morley experiment

Epsilon_0: the vacuum permittivity

10 / 20

What would be the energy per beam of a future proton collider at 100 TeV in the center of mass?

100 TeV

50 TeV

25 TeV

11 / 20

What is the difference between the Galilean and the Lorentz transformations?

Lorentz transformation includes an additional factor to ensure that the speed of light is the same in all referentials.

Galilean transformation uses greek letter, Lorentz transformation uses latin letter.

None, it is the same.

12 / 20

For a source moving in the horizontal plane, what is the angle with respect to the vertical (perpendicular) plane where electric field lines are more concentrated at relativistic velocities?

1/gamma

gamma

1/alpha

beta

10 degrees

alpha

1/beta

13 / 20

What is the relation linking the energy (E) , the momentum (p) and the rest mass (m0)?

p=mV

F=qE

E=m0c^2

E^2 = p^2c^2 + m0^2c^4

E = p c + m0c^2

14 / 20

What is the effect of accelerating charged particles which already move almost at the speed of light?

Their velocity and their mass increases

Their velocity increases, not their mass

Neither their velocity nor their mass increases

Their mass increases, not their velocity

15 / 20

What happens to the velocity and the energy of a relativistic charged particle when we continue to accelerate it?

Its energy continues to increase, its velocity becomes almost constant

Both energy and velocity become almost constant

Both energy and velocity continue to increase.

Its velocity continues to increase, its energy becomes almost constant

16 / 20

What is the maximum speed of an object?

It depends on the referential

The speed of light

The speed of sound

Twice the speed of light

17 / 20

In the LHC, protons are injected at a total energy of 450 GeV and accelerated up to 7 TeV. Why should the LHC be called a “massificator” and not an accelerator? (several answers accepted)

Because "accelerator" is a trademark of a car manufacturer.

Because the speed of the particles almost does not change during the acceleration process, it is their mass that increases.

Because it uses heavy particles.

Because the name "accelerator" is reserved for specific applications.

18 / 20

What are the 2 postulates of Special Relativity? (select all relevant answers)

The speed of sound is a fixed constant of the universe

Space and time have no existence out of our conscience

The laws of physics are the same wherever tested in all inertial (or Galilean) frames

Time and length are the same in all referentials

The speed of light is a fixed constant of the universe

19 / 20

Does the electric field maintain the spherical symmetry when charges are moving?

No

Yes

20 / 20

In the relativistic Doppler effect, the observed frequency from an observer going towards the light source, is

increased by the relativistic factor beta

increased by the relativistic factor gamma

decreased by the relativistic factor beta

decreased by the relativistic factor gamma

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Quiz for the JUAS 2024 students – Special relativity

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