1.5- PARTICLE INTERACTIONS

Question 1

What can we use to measure forces?

Answer 1

newton meters and force sensors

Question 2

What happens when a single force acts on an object?

Answer 2

it changes the momentum of the object

Question 3

What is the momentum of an object?

Answer 3

its mass multiplied by its velocity

Question 4

What happens when two objects interact?

Answer 4

exert equal and opposite forces on each other

Question 5

What is transferred through these forces?

Answer 5

momentum

Question 6

What is an example of this transfer of momentum?

Answer 6

two protons that approach each other. they repel each other and move away from each other

Question 7

Which American Physicist worked out in detail about the transfer of momentum?

Answer 7

Richard Feynman

Question 8

What did Richard Feynman say?

Answer 8

the electromagnetic force between two charged objects is due to the exchange of virtual photons

Question 9

Why did Richard describe them as virtual photons?

Answer 9

we can’t detect them directly

Question 10

Using what would be intercept the virtual photons and what would happen?

Answer 10

using a detector

would stop the force acting

Question 11

analogy for two like-charged particles

Answer 11

two people on skateboard
one of them throws ball at other
thrower recoils when the ball leaves their hand and other person recoils when they catch ball

Question 12

What does the ball transfer in the analogy?

Answer 12

momentum from the thrower to the catcher so repel each other

Question 13

What is the difference between the analogy and the exchange of a virtual photon between two like-charged particles?

Answer 13

we can’t detect the virtual photon

Question 14

What does the ball analogy not work for?

Answer 14

for two oppositely charged particles

Question 15

What would the ball have to be changed to for two oppositely charged particles?

Answer 15

a boomerang so the thrower and catcher attract each other

Question 16

What does the strong nuclear force do?

Answer 16

hold the neutrons and protons in the nucleus together

Question 17

What does the weak nuclear force do?

Answer 17

cause a neutron to changed into a proton in beta (-) decay or proton to change into neutron in beta (+) decay

Question 18

What happens in both beta (+) and beta (-) decay?

Answer 18

a new particle and a new antiparticle are created

Question 19

What is something about the particle and antiparticle released in beta decay?

Answer 19

not a corresponding particle-antiparticle pair

one is an electron or positron
other is neutrino or antineutrino

Question 20

How often do neutrinos and antineutrinos interact?

Answer 20

hardly interact with each other

Question 21

Examples of neutrino and antineutrino interactions (2)

Answer 21

neutrino can interact with a neutron and make it change into a proton. beta(-) particle (electron) created and emitted as a result of change

antineutrino can interact with a proton and make it change into a neutron. beta (+) particle (positron) created and emitted as a result of change

Question 22

What are the neutrino and antineutrino interactions due to?

Answer 22

the exchange of particles referred to as W bosons

Question 23

3 things about W bosons

Answer 23

have a non-zero rest mass
have a very short range of no more than about 0.001fm
positively charged or negatively charged

Question 24

How were W bosons first detected?

Answer 24

using the 2km diameter Super Proton Synchrotron at CERN in Geneva

Question 25

What happened during the experiment at CERN?

Answer 25

protons and antiprotons at very high energies were made to collide and annihilate each other
at sufficiently high energies, annihilations produce W bosons as well as photons

Question 26

What role does W bosons play in beta decay?

Answer 26

W boson meets neutrino and changes it to a beta(-) particle (electron)
W boson meets antineutrino and changes it to a beta(+) particle (positron)

Question 27

What happens to the W boson if no neutrino or antineutrino is present?

Answer 27

W(-) boson decays into a beta(-) particle and antineutrino

W(+) boson decays into a beta (+) particle and neutrino

Question 28

What is electron capture?

Answer 28

sometimes a proton in a proton-rich nucleus turns into a neutron as a result of interacting through the weak interactions with an inner-shell electron from outside the nucleus

Question 29

What does the W(+) boson change the electron to in electron capture?

Answer 29

a neutrino

Question 30

When can a similar change to that of electron capture happen?

Answer 30

when a proton and electron collide at very high speed

Question 31

For an electron with sufficient energy what can the overall change occur due to?

Answer 31

W(-) exchange from proton to proton

Question 32

What are the photon and W boson known as?

Answer 32

force carriers as they are exchanged when the electromagnetic force and weak nuclear force act representatively

Question 33

What is the pion known to be?

Answer 33

exchange particle of the strong nuclear force

Question 34

What do scientists think the carrier of the force of gravity is?

Answer 34

graviton- bit it has yet to be observed