Question regarding particle tracks

6

My issue is in question 18b

I don't understand any of it, how is it that we determine that the particle moves in a clockwise direction via change in radius or by energy transfer? An elaborate explanation would be appreciated.

Reply 1

Nitrotoluene

11

Original post

by tigrispanthera

My issue is in question 18b
I don't understand any of it, how is it that we determine that the particle moves in a clockwise direction via change in radius or by energy transfer? An elaborate explanation would be appreciated.

To understand that anti-muon in the picture that goes clockwise, think about these things: how the radius of the path changes and how the particle loses energy.
1. Changing Radius
Particles in a magnetic field move in circles or spirals. The size of the circle depends on the speed of the particle and the strength of the field which is shown in the formula.
When the radius gets smaller, the particle is slower.
For a charged particle moving in a magnetic field, the radius of the circular path is given by:

r = (m x v) / (q x B)

Where:
r = radius of the particle’s circular path
m = mass of the particle
v = speed of the particle (perpendicular to the magnetic field)
q = electric charge of the particle
B = magnetic field strength
2. Energy Loss
The anti-muon loses energy by collisions with the environment, e.g. atoms. This takes away its kinetic energy.This energy loss affects its speed and momentum.
So, the clockwise thing is because the radius is shrinking and it is running out of energy, thus the spiral becomes tighter.
In short, the anti-muon goes clockwise because:
First, its trajectory gets smaller as it loses energy.Second, it slows down as it loses energy.
This is a connection of a particle's motion with energy considerations.
Ciao,
Sandro

(edited 2 months ago)

Reply 2

tigrispanthera

OP

6

Original post

by Nitrotoluene

To understand that anti-muon in the picture that goes clockwise, think about these things: how the radius of the path changes and how the particle loses energy.
1. Changing Radius
Particles in a magnetic field move in circles or spirals. The size of the circle depends on the speed of the particle and the strength of the field which is shown in the formula.
When the radius gets smaller, the particle is slower.
For a charged particle moving in a magnetic field, the radius of the circular path is given by:

r = (m x v) / (q x B)

Where:
r = radius of the particle’s circular path
m = mass of the particle
v = speed of the particle (perpendicular to the magnetic field)
q = electric charge of the particle
B = magnetic field strength
2. Energy Loss
The anti-muon loses energy by collisions with the environment, e.g. atoms. This takes away its kinetic energy.This energy loss affects its speed and momentum.
So, the clockwise thing is because the radius is shrinking and it is running out of energy, thus the spiral becomes tighter.
In short, the anti-muon goes clockwise because:
First, its trajectory gets smaller as it loses energy.Second, it slows down as it loses energy.
This is a connection of a particle's motion with energy considerations.
Ciao,
Sandro

Why clockwise specifically? Why not anti-clockwise? I understand that the radius decreases because of loss of Kinetic energy and thus loss of speed but why is it clockwise specifically that the question makes a big deal out of?

Is it because the particle is already in that motion before it decays? Maybe I'm focusing too much on the clockwise part.

Reply 3

Eimmanuel

Study Forum Helper

15

Original post

by tigrispanthera

Why clockwise specifically? Why not anti-clockwise? I understand that the radius decreases because of loss of Kinetic energy and thus loss of speed but why is it clockwise specifically that the question makes a big deal out of?

Is it because the particle is already in that motion before it decays? Maybe I'm focusing too much on the clockwise part.

Part (c) of the question "tells" you the reason. :smile:

Reply 4

Nitrotoluene

11

Original post

by tigrispanthera

Why clockwise specifically? Why not anti-clockwise? I understand that the radius decreases because of loss of Kinetic energy and thus loss of speed but why is it clockwise specifically that the question makes a big deal out of?
Is it because the particle is already in that motion before it decays? Maybe I'm focusing too much on the clockwise part.

I agree with you.
I suppose that you may be concentrating too much on the clockwise aspect, as the given text only tells us how we know its direction of motion in time and not why the motion is clockwise (inward spiral).
The passage takes the radius is shrinking (after energy loss) as a ground to indicate the particle's direction of travel in time (it came from the large radius and is going to the small radius).
The clockwise or anti-clockwise side of the orbit in question come from the sign of the charge and the direction of the external magnetic field, both of which are not mentioned in the text:

•

Particle's electric charge (q).

•

The direction of the magnetic field (B).
Ciao,
Sandro

Question regarding particle tracks

Quick Reply

Related discussions

Articles for you

How The Student Room is moderated