Motion Of Particles

Question 1

What is circular motion

Answer 1

Velocity is the speed and direction
If an object travels in a circle it is constantly changing direction so it’s accelerating
So there must be a resultant force
This force acts towards the centre of the circle
The force that keeps the thing travelling in a circle is centripetal force

Question 2

What are particle accelerators

Answer 2

Devices that accelerate particles in a circular motion

Question 3

How are charged particles affected by a magnetic field

Answer 3

The force of the charged particle in a magnetic field is always perpendicular to its direction of travel
So the particles path curves
The direction of the force depends on its charge so positive and negative charges will move in opposite directions
Usually the particles will spiral because they lose energy and slow down as they interact with other particles
The less energy the more curved the path
Magnetic fields are used to make charged particles move in circular or spiral paths in a particle accelerator

Question 4

What is a cyclotron

Answer 4

It is a particle accelerator that uses a magnetic field to accelerate particles to very high energies along circular paths

Question 5

How do cyclotrons work

Answer 5

The charged particles e.g. Protons start in the Center
The cyclotrons use two hollow semi circle electrodes to accelerate the particles across a gap
An alternating potential difference is applied between the two electrons as the particles are attracted from one side to the other their energy increases
The magnetic field is used to keep the particles in a circular motion but makes the particles spiral outwards as their energy increases

Question 6

How are some radioactive isotopes formed

Answer 6

By bombarding stable elements with protons
The proton is absorbed by the nucleus increasing the proton number meaning you get a new element
This happens in a cyclotron because the particle needs lots of energy

Question 7

What are positron emitters used for

Answer 7

They are used in pet scans so must have a short half life so that the patients exposure is limited

Question 8

How is fluorine-18 made using oxygen 18

Answer 8

O(18 8) + p (1 1) -> f (18 9) + n(1 0)

Question 9

How is carbon 11 made using nitrogen 14

Answer 9

N (14 7) + p (1 1) -> c (11 6) + he (4 2)

Question 10

How is carbon 13 made using oxygen 16

Answer 10

O(16 8) + p (1 1) -> N (13 7) he (4 2)

Question 11

How are particle accelerators used to find out more about the universe

Answer 11

They use them to smash particles into each other at high speeds so they can see what happens and what kind of radiation is given off this gives us more clues about how the universe works so we can get better explanations

Question 12

What is the large hadron collider

Answer 12

It’s the largest most powerful collider it is used to try and recreate extreme conditions just like after the Big Bang by colliding two beams of protons at fast speeds

Question 13

Momentum

Answer 13

Mass x velocity

Question 14

How does conservation of momentum work when the two things bounce off each other

Answer 14

The two masses collide and there is two new velocities similar to when a fast moving neutron hits a nucleus and bounces off again

Question 15

How does conservation of Momentum work when two objects join

Answer 15

The two masses and velocities join to make one mass and one velocity
Similar to when a neutron or proton collides with an atom and Is absorbed into the nucleus

Question 16

How is momentum conserved in an explosion

Answer 16

The mass splits and creates two new velocities

Like a particle being emitted from a nucleus

Question 17

What is a conservation of momentum

Answer 17

Total momentum after is equal to the total momentum before

Question 18

What is an elastic collision

Answer 18

Where the momentum is conserved and kinetic energy is conserved so no energy is lost

Question 19

What is an in elastic collision

Answer 19

Some of the kinetic energy is converted into another form during the collision
When you drop a bouncy ball it bounces again but not as high because some of the kinetic energy is lost so there’s less gravitational potential so it can’t get as high

Question 20

What is annihilation

Answer 20

When an particle meets an anti particle all of the mass of both particles is converted to energy which is given off in gamma rays

Question 21

How is momentum conserved in annihilation

Answer 21

The particles have the same mass and opposite velocities so the total momentum before collision is 0
Momentum is always conserved so the gamma rays produced must have a total momentum of 0
So normally two gamma rays are produced with the same energy but opposite velocities
The charge is also conserved

Question 22

E =

Answer 22

M X c2
Energy in Joules equals mass in kg times speed of light squared (3x10power8) squared
Einstein Said that mass is a Form of Energy so it can be converted to other forms of energy and vice versa

Question 23

How is annihilation used in pet scans

Answer 23

A positron emitting isotope is put into a patient and the positrons collide with electrons in organs causing annihilation and emit high energy gamma rays
More of the radioactive isotope is taken up in the cancer cells than normal cells so more gamma will be detected
The location of a tumour can be found by detecting the pairs of gamma rays and finding where their paths lead triangulation DNA be used to find this