1.5 Particle Interactions

Question 1

How can we measure forces

Answer 1

By using newtonmeters and force sensors

Question 2

What changes in an object when a single force acts on it

Answer 2

Changes the momentum of the object

It is its mass multiplied by its velocity

Question 3

What happens when two objects interact

Answer 3

They exert equal and opposite forces on each other

Question 4

What happens if two protons approach each other

Answer 4

They repel each other and move away from each other

Question 5

What did Richard Feynman work out about electromagnetic forces between two charged objects

Answer 5

Said it was due to the exchange of virtual photons

Question 6

What can be drawn to show the electromagnetic force between two protons

Answer 6

A Feynman diagram

Question 7

Do the lines in a Feynman diagram represent the paths of the particles

Answer 7

NONONO

Question 8

What holds the neutrons and protons in a nucleus together

Answer 8

The strong nuclear force

Question 9

What force causes aw neutron to change into a proton in β- decay or a proton to change into a neutron in + decay

Answer 9

The weak nuclear force

Must be weaker than the strong nuclear force otherwise it would affect stable nuclei

Question 10

What is formed in β+ and β- decay

Answer 10

A new particle and new antiparticle
NOT a corresponding particle-antiparticle pair, as one is an electron or a positron and the other is a neutrino or an antineutrino

Question 11

Do neutrinos and antineutrinos interact with other particles

Answer 11

Hardly

Question 12

What happens when a neutrino interacts with a neutron

Answer 12

Makes it change into a proton

β- particle (electron) is created and emitted as a result of the change

Question 13

What happens when an antineutrino interacts with a proton

Answer 13

Makes it change into a neutron

β+ particle (a positron) is created and emitted as a result of the change

Question 14

What are the interactions between a neutrino and neutron, and antineutrino and proton due to

Answer 14

The exchange of particles called W bosons

Question 15

W bosons:

Answer 15

Have a non-zero rest mass
Have a very short range of no more than about 0.001 fm
Are positively charged (W+ boson) or negatively charged (W- boson)

Question 16

Discovery of the W boson

Answer 16

First detected directly in 1983 by scientists at CERN
Protons and antiprotons at very high energies made to collide and annihilate each other.
High energies, W bosons and photons produced
β particles from W boson decays detected exactly as predicted

Question 17

What does the W- boson decay into

Answer 17

A β- particle and an antineutrino

Question 18

What does the W+ boson decay into

Answer 18

β+ particle and a neutrino

Question 19

Sometimes a proton in a proton-rich nucleus turns into a ______ as a result of interacting through the weak interaction with an ______-______ electron from outside the nucleus (______ ______).

Answer 19

Neutron
Inner-shell
Electron Capture

Question 20

Why are the photon and W boson known as force carriers

Answer 20

As they are exchanged when the electromagnetic force and the weak nuclear force act respectively