Summary Need help with A2 physics Unit 5? This document will give you the best revision and help you as you solve the past question papers
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Module
Physics
Institution
6
Book
Edexcel A Level Physics Student Book 2
Salient features of this note:
* It is always updated with questions from recent past papers
* It deals mainly with questions from past papers and leaves out
unnecessary details
* List of difficult questions from past papers which will help you
with last minute revision
* Detailed explanation...
Content:
1. List of difficult questions
2. Discussion of questions from Past Papers
i) Simple Harmonic Motion
ii) Nuclear Physics and Binding Energy
1. List of difficult questions
● New Syllabus Unit 4 exam took place in Jan 2020, Oct 20 and Jan
21.
● New syllabus Unit 5 took place in October 2020 only.
● Sample Assessment Material for the New Syllabus. You can find it on
the Edexcel Website: 3, 15b)iii) (Very very important)
● October-Nov 2019: 3,6 (Damping force increases with the amplitude
of oscillation), 13c) , 15a) *, 16c), 17a) , 18a)iii), b)*, 19b)iii)
● May 2019 (old): 4(it’s probably the only MCQ on photographic
film),6,9(another unique MCQ on parallax method) ,10 (you need to
have some idea about the temperature and luminosity of red giants,
white dwarfs and black dwarfs)
● Jan 2019 (old): 6,7,8, 15b)i)ii) & iii) (an innovative sum on simple
harmonic motion)
● October 2018 (old): 4,
● June 2018 (old): 6,8
Discussion of questions from past papers
Simple Harmonic Motion (SHM)
Prepared by Ridwan Abrar
,Formulae:
There are 2 possible cases for the SHM graphs:
If particle starts from amplitude (peak point) If particle starts from equilibrium
x = A cos (ωt) x = A sin (ωt)
v= − Aω sin (ωt) v = Aω cos (ωt)
a = − Aω 2 cos (ωt) a = − Aω 2 sin (ωt)
a = − ω 2 x , where x = displacement measured from equilibrium position.
Then we have a formula for the cases when velocity and acceleration becomes maximum.
v max = ωA and amax = ω 2 A
PE = ½ kx2 and KE = ½ mv2
Also the formula for total energy is
1 2
T otal energy = 2 kA
Definition of SHM (2 marks)
● Acceleration/force is directly proportional to displacement from equilibrium position
● Acceleration/force is always in opposite direction of displacement
Or, Acceleration/force is always directed towards the equilibrium position
Graphs of SHM
Acceleration is a sine function of t. Say a = sin(wt)
So, as a=dv/dt, to get the velocity function v, we are to integrate it.
Prepared by Ridwan Abrar
, And integration of sine function results in -cos function.
U can use desmos app to get the plots easily
Resonance: Large amplitude forced vibration which occurs when the frequency of the driving system
matches the natural frequency of the driven system.
(To avoid resonance, mechanical dampers are used which absorb the total energy of the system and
dissipate it elsewhere)
Free vibration: When an object oscillates without the influence of any external medium, it is known as
free vibration.
Forced vibration: When an object oscillates under the influence of an external source, it is known as
forced vibration.
Definition of damping/ tuned mass dampers
Damping is a system which absorbs energy from a system. Dampers are frequently used to avoid
resonance and large amplitude vibrations in a system where it could cause damage. (for example in a
rolling bridge)
The photograph shows tuned mass dampers which were fitted to the bridge. They are tuned to the
natural frequency of oscillation of the bridge.
Discuss how the tuned mass dampers reduce the amplitude of oscillation of the bridge and
explain why they must be very heavily damped. (3 marks)
● The springs/ damper absorb energy from the bridge
● because the springs deform/ oscillate with the natural frequency of the bridge
● hence there is an efficient / maximum transfer of energy
● Springs/ dampers must not return energy to the bridge/ must dissipate the energy
When a tuning fork is struck with a rubber hammer, a pure sound of fixed frequency is produced.
The photograph shows a tuning fork connected to a wooden sounding box. (Reference: Jan 12,
Q14)
● The sounding box amplifies the sound produced when the tuning fork is struck
● The sound lasts for a shorter time than if the tuning fork were to be struck identically than
without the sounding box.
Explain these observations. (5 marks)
● Resonance is the large amplitude forced vibration when the frequency of the driving system
matches the natural frequency of the driven system
● The sounding box is forced to vibrate at the frequency of the tuning fork
● Tuning fork and sounding box have similar natural frequencies
● Energy transferred from the tuning fork to the sounding box
● The sounding box sets a large mass/ amount/ volume of air into vibration
● Hence the sounding wave produced in the air has a large amplitude
● Sounding box dampens the vibration of the tuning fork
● Larger rate of energy transfer to the air means the vibrations persist for a shorter time
For the SHM part, please check the stationary waves in a string, stationary waves in open and
closed tube from AS. These frequently make it up to the exam. Please review that part.
Prepared by Ridwan Abrar
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