6 MARKERS

Question 1

(6) A= Force 1 ►(OBJECT)◄ Force 2
B= Force 1 ▼(OBJ) ►(OBJ) Force 2►
Analyse both collisions in terms of momentum and kinetic energy.

Answer 1

Diagram 1
 Moving in opposite directions before collision
 inelastic collision
 stationary after collision
 momentum zero after collision
 (therefore) total momentum must have been zero
before collision
 (therefore) cars were moving at the same speed in
opposite directions (assuming cars have equal mass)
 both cars had kinetic energy before the collision
 KE zero after collision
 KE converted into heat, sound, elastic potential
energy etc.
Diagram 2
 Elastic collision / almost elastic collision
 Momentum conserved
 Momentum transferred from first to last sphere
 KE conserved / almost conserved
 (because)last sphere reaches same height as first
sphere
 Three spheres always have zero momentum
 Small amount of energy transferred to sound/heat

Question 2

(6 )Compare the design and use of particle accelerators used in international
scientific research with particle accelerators used in hospitals.

Answer 2

particle accelerators use:-
 charged particles
 magnetic fields
 high frequency alternating voltages
 collisions
 centripetal force
hospital particle accelerators
 cyclotrons
 small, size of a garage
 fast moving particle hit targets
 particles absorbed by nuclei
 produce isotopes with short half lives
 only a few people needed to work them
research particle accelerators
 cyclotrons, synchrotrons,
 Large Hadron Collider, CERN
 very large, LHC more than 2 km across
 use superconducting electromagnets
 accelerate particles to close to the speed of light
 use hundreds of research scientists
 make particles collide
 try to discover new particles (Higgs Boson)

Question 3

(6) Compare the use of electromagnetic radiation in endoscopes and in one other
diagnostic device.

Answer 3

Diagnostic devices
• CAT scanners
• Fluoroscopes
• Thermal imagers / IR thermometers
• Pulse oximeters
• PET scanners
• X-ray machines
• Gamma cameras
Link to electromagnetic radiation
• Endoscopes use TIR of light in optical fibres
• CAT scanners X- rays and computer to generate 3D
images
• Fluoroscopes use X- rays and a video camera
• Thermal imagers use infrared emitted by a body
• IR / red LEDs used to measure oxygen levels
• PET scanners detect radiation emitted by electronpositron
annihilation
• Gamma cameras detect gamma rays from radioactive
sources
Other factors for comparison
• Safety
• Ease of use
• Frequency / wave length
• Intensity
• Penetration
• Ionising / non-ionising

Question 4

(6) The diagram shows an electrocardiogram (ECG) trace with values given for the
horizontal and vertical scales used.
Describe how the characteristic shape of the curve and the distance between
peaks relates to the way the heart works.

Answer 4

standard labelling for electrocardiogram signal
 pattern shows heart action
 all shapes are the same so no heart irregularity
 patterns shows the parts of the heart pumping blood
 pattern produced reflects the electrical activity of the heart
 changes in the shape can show weaknesses in different
parts of the heart ( heart attacks)
 the trace shows potential differences across different parts
of the heart when the muscles contract and relax
 action potentials ( electrical signals) originate in the right
atrium of the heart
 P wave shows muscle contraction spreading through the
atria (depolarisation)
 QRS shows the ventricles contracting to pump blood to
lungs and the rest of the body
 T wave is repolarisation when ventricles fill with blood
Distance between peaks
 shows heart rate.( 60 to 90 beats per minute considered
normal)
 the time for one beat of the heart is represented by the
distance between the peaks (could be shown on diagram)
 one beat is 0.78s to 0.82s
 frequency of 1.25Hz to 1.3 Hz
 beats per minute 74 to 80

Question 5

(6) Explain how long sight and short sight are different from normal sight and how one of these defects can be corrected.

Answer 5

• normal eye image forms on retina
• for all distances of objects
• short sight
• (clear) image of a distant object forms inside the eye / in front of retina
• corrected using diverging lens
• diverging the light / makes image distance longer
• long sight
• (clear) image of near object forms “beyond” the retina
• corrected using converging lens
• converging the light / makes image distance smaller

Other methods of correction include
• contact lenses which change the curvature of the cornea
• laser correction changes curvature of cornea

Question 6

(6) Describe, in terms of quarks, how ȕ+ particles are emitted from the nuclei of some
atoms and ȕ– particles are emitted from the nuclei of others.

Answer 6

 protons and neutrons are made up of quarks
 quarks can change (flavour)
 proton made up of uud
 neutron made up of udd
 for β+ a u changes to a d
 for β-
 a d changes to a u
 for β+ a p changes to a n
 for β-
 a n changes to a p