Question 1

Because of time dilation,if a twin goes on a trip in a high-speed rocket ship,when she returns home she will be younger than her twin sister who did not go on the trip.

Accepted Answer

According to the theory of relativity, time appears to run slower in a moving frame of reference than in a stationary one. Therefore, a person traveling in a high-speed rocket ship will experience time at a slower rate than someone who is stationary on Earth. This means that when the twin who went on the trip returns home, she would have aged less than her twin sister who remained on Earth, making her younger.

Question 2

A fermion has integral spin.

Accepted Answer

Fermions have half-integer spins, such as 1/2, 3/2, etc., while particles with integral spins are bosons.

Question 3

Because of the equivalence of energy and mass,a gamma ray,which is a high energy photon,can "disappear," and in its place there will be produced an electron and a positron,which both have mass.

Accepted Answer

This phenomenon is known as pair production, where a high energy photon (such as a gamma ray) can interact with a nucleus or an electron in a material and be converted into a particle-antiparticle pair (electron and positron) due to the conservation of energy and momentum. This demonstrates the equivalence of energy and mass, as the energy of the photon is now converted into the mass of the two particles.

Question 4

Short range interactions generally have carrier particles of greater mass than those for long range interactions.

Accepted Answer

Short range interactions, such as the strong nuclear force and weak nuclear force, are carried by particles with greater mass, such as gluons and W and Z bosons. Long range interactions, such as electromagnetism and gravity, are carried by particles with very low mass, such as photons and gravitons.

Question 5

Because of their short lifetimes,very few muons that are produced in the upper atmosphere at high speeds should be observed at the surface of the Earth.Yet we detect large numbers of muons at ground level because of the Pauli exclusion principle.

Accepted Answer

The large number of muons detected at ground level is due to time dilation, a relativistic effect, not the Pauli exclusion principle.

Question 6

Special relativity predicts that the length of a moving object will be elongated in the direction of motion.

Accepted Answer

Special relativity predicts that the length of a moving object will be contracted, not elongated, in the direction of motion, a phenomenon known as length contraction.

Question 7

Leptons are built out of quarks.

Accepted Answer

Leptons are elementary particles and not built out of quarks. Quarks are building blocks of protons and neutrons, which are composite particles.

Question 8

Since the rest energy of an electron and its antiparticle a positron is 0.511 MeV,a gamma ray must have an energy larger than 1.022 MeV to produce an electron-positron pair.

Accepted Answer

This statement is true according to the conservation of energy and momentum in particle interactions. The energy of a gamma ray photon must be greater than the combined rest mass energy of an electron and a positron to create them from the photon's energy. The total rest mass energy of an electron and a positron is 2 × 0.511 MeV = 1.022 MeV. Therefore, a gamma ray photon with energy less than 1.022 MeV cannot create an electron-positron pair.

Question 9

If a 1-kg mass is completely converted into energy,the amount of energy released would be 9 × 10¹⁶ J.

Accepted Answer

This is based on Einstein's famous equation E=mc², where E is energy, m is mass, and c is the speed of light. Substituting 1 kg for m and solving for E gives E=9 × 10¹⁶ J.

Question 10

The four fundamental forces in nature are the strong,weak,electromagnetic,and gravitational interactions.

Accepted Answer

This statement is true. The four fundamental forces in nature are the strong, weak, electromagnetic, and gravitational interactions.

Question 11

Hadrons are particles that interact via the strong force.

Accepted Answer

This is true. Hadrons are particles that are made up of quarks and interact via the strong force. Examples of hadrons include protons, neutrons, and mesons.

Question 12

A boson has half-integral spin.

Accepted Answer

Bosons have integral spin (0, 1, 2, ...), while fermions have half-integral spin (1/2, 3/2, ...).

Question 13

Because of the equivalence of mass and energy,an electron and a positron,which are two massive particles,can annihilate when they come together to produce two photons,which have no mass.

Accepted Answer

According to the principle of mass-energy equivalence (E=mc²), any mass can be converted into energy and vice versa. When an electron and a positron come together, they can annihilate and the mass of both particles is converted into energy in the form of two photons (gamma rays), which have no mass. Therefore, the statement is true.

Question 14

Special relativity predicts that moving clocks run slow.

Accepted Answer

Special relativity predicts time dilation, which means that clocks moving relative to an observer will appear to run slower than clocks at rest with respect to that observer. This effect has been experimentally verified multiple times.

Question 15

Bosons are force-carrying particles.

Accepted Answer

The answer of Bosons are force-carrying particles....

Question 16

Any particle with spin obeys the Pauli exclusion principle.

Accepted Answer

The Pauli exclusion principle applies specifically to fermions, which are particles with half-integer spin, not to all particles with spin. Bosons, which have integer spin, do not obey this principle.

Question 17

The speed of light is a relativistically invariant quantity.

Accepted Answer

The speed of light is a constant value that is the same for all observers, regardless of their relative motion, according to the theory of relativity. This means that it is a relativistically invariant quantity.

Question 18

According to special relativity,at speeds approaching the speed of light,the kinetic energy of a moving object is not equal to 1/2 mv².

Accepted Answer

In special relativity, the kinetic energy of an object moving at speeds close to the speed of light is given by a different formula that accounts for relativistic effects, not the classical 1/2 mv².

Question 19

Einstein's famous equation E = mc² is a statement of the equivalence of energy and the square of the speed of light.

Accepted Answer

Einstein's famous equation is actually E=mc², not E=mc². However, it is true that this equation expresses the equivalence of energy and mass (not the square of the speed of light).

Question 20

A lepton interacts via the strong interaction.

Accepted Answer

Leptons do not interact via the strong interaction. They only interact via the weak and electromagnetic interactions.

Quiz 12: Special Relativity and Elementary Particles