4.5 Forces of Nature

Question 1

What are the four forces and interactions that occur between particles?

Answer 1

Strong force
Electromagnetic force
Weak nuclear force
Gravity

Question 2

What is the force between the particle mediated (or transmitted) by?

Answer 2

Particles called bosons.

Question 3

When does strong force occur?

Answer 3

In the nucleus between quarks and hadrons.

Question 4

When does electromagnetic force occur?

Answer 4

With charged particles.

Question 5

When does weak nuclear force occur?

Answer 5

Beta decay of nucleus.

Question 6

When does gravitational force occur?

Answer 6

Due to mass.

Question 7

What is the particle responsible for strong force?

Answer 7

Gluons (pions).

Question 8

What is the particle responsible for electromagnetic force?

Answer 8

Photons- these have no mass and so leads to the force having an infinite range.

Question 9

What is the particle responsible for weak nuclear force?

Answer 9

Bosons.

Question 10

What is the particle responsible for gravitational force?

Answer 10

Gravitons?

Question 11

What is the relative ranges for the forces?

Answer 11

Strong
Weak
Electromagnetic & Gravitational (infinite)

Question 12

What is the relative strengths of the forces?

Answer 12

Strong
Electromagnetic
Weak
Gravitational

Question 13

What carries the force between particles?

Answer 13

The bosons.

Question 14

What fixes the range of the force?

Answer 14

The mass of the exchange particle.

Question 15

Why is it the exchange particle cannot be detected during its transfer between the particles?

Answer 15

This would mean that it would no longer be acting as the mediator of the force between the particles.

Question 16

The larger the rest mass of the exchange particle the…

Answer 16

Lower the time it can be in flight without it being detected and therefore the lower the range of the force.

Question 17

The strong force is the strongest of the force, what does its strength enable it to do?

Answer 17

Overcome the large repulsive forces acting between the charged protons in the nucleus or between the quarks that make up the protons.

Question 18

When is the strong force attractive?

Answer 18

At nuclear distances.

Question 19

When is the strong force repulsive?

Answer 19

At very small distances.

Question 20

What is the electromagnetic force?

Answer 20

The familiar force that we find exerted between charged particles at rest or in motion.

Question 21

What happens in beta decay?

Answer 21

A neutron decays to a proton.
A W-boson is exchanged as a quark changes from down to up.
The W-boson then immediately decays into an electron and an electron anti-neutrino.

Question 22

What does the fact that the W and Z particles responsible for weak interactions are very massive mean?

Answer 22

This leads to the force they give rise to being very short range, only about 0.01 of the diameter of a proton.

Question 23

What interaction is the only way in which a quark can change into another quark, or a lepton into another lepton?

Answer 23

The weak interaction.

Question 24

What is the weakest of the forces?

Answer 24

Gravitational force.

Question 25

What is long range and the dominant force that operates within and between galaxies?

Answer 25

Gravitational force.

Question 26

What is the electroweak force?

Answer 26

At high energies it has already been found that the electromagnetic force and the weak nuclear force cannot be distinguished. They merge to form one single force, the electroweak force.

Question 27

Order of strength of the forces.

Answer 27

Strong force
Electromagnetic force
Weak nuclear force
Gravity