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oh and the space between the wavefronts in fig. 7.1 should be same since its only reflection so only direction changes
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GUYS HELP 4 PHYSICS PAPER 3
- Thread starter Mohammed Khalaf
- Start date
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- 74
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after like 3 years ov physics..this might sound stupid.....but can anyone please telme dat are sound waves longitudinal or transverse???
also can u list a few examples ov both...?????
also can u list a few examples ov both...?????
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Thanks for the help guys <333
so I planned to do something for u all <3
Here r some important formulas for physics paper :
Density = mass/volume
Speed = distance/time
Acceleration = Change in velocity (v-u)/time
Force = mass x acceleration
Weight = mass x g (10 m/s2) OR (10 N/kg)
Moment of force = force x perpendicular distance from a point
Load = spring constant x extension
Pressure = force/area
Pressure in liquid = density x g x height
Compressing gases ( Pressure 1 x Volume 1 = Pressure 2 x Volume 2 )
Work Done = Force x Distance moved
Gravitational Potential Energy = mass x g x height
Kinetic energy = 1/2 x mass x velocity2
Energy transferred 1 = mass x specific heat capacity x temperature change
Energy transferred 2 = mass x specific latent heat
Power = work done/time = energy transferred/time
Efficiency = useful work done/total energy input
Waves = frequency x wavelength
Frequency = 1/period (time)
Refractive index = sin of incidence angle/ sine of refracted angle
Total Internal reflection (sin of critical angle) = 1/reflective index
Charge = current x time
Resistance = Voltage / current
Voltage = Current x Resistance
Resistors in series = Resistor 1 + Resistor 2
Resistors in parallel = 1/Resistor 1 + 1/Resistor 2
Electrical Power = Voltage x current
Electrical energy = Power x time OR Voltage x current x time
Transformers = Output Voltage 2/Input Voltage 1 = Output turns 2/Input turns 1
Current of Transformers = Current 1 x Voltage 1 = Current 2 x Voltage 2
u really need to do this
GENERAL RULES FOR DOING PHYSICS EXAM PAPERS
Read all of the parts of a question before answering it.
Pay attention to the number of marks on offer (eg for 3 marks, you must say at least three things).
1 mark questions saying 'State' or 'Recall' require short, simple answers.
Learn all definitions and formulas word-for-word.
Give enough detail in your answers. State the obvious eg a force is a push or a pull.
Show that you can use Physics vocabulary whenever you can.
Note the action words in the question (and answer accordingly): State; Explain; Complete; Describe; Use (the graph); Suggest; Evaluate
Part questions are usually on a single topic eg the answer to part (a) feeds into (b).
Stay aware of the time (1 mark per minute). If you get stuck, move on and return if you have time at the end.
Don't be afraid to physically act out the electromagnetism hand rules in the exam.
Never leave a question blank. If nothing else, write down relevant formulas or definitions.
As you finish a question, quickly re-read your answer to make sure it makes sense.
Don't leave early. Check and re-check your answers.
After the exam, don't waste time discussing your answers. Look ahead to the next paper.
Calculations: always show your working: there are many marks for this even if the answer is wrong.
These are the stages: Formula - Rearrange - Information - Substitute - Calculate - Answer - Unit
Underline: Show your final answer clearly highlighting or underlining.
Significant figures: There are marks for getting this right. Every answer should be given to the correct number of sf (the same sf as the numbers given in the question). eg 5.2*9.8 = 51 (2 sf). It is a good idea to state the sf to show that you know about it.
Equations: if you are asked to write one down, use words not just symbols.
Rounding: if you are asked to show a quantity is 'approximately equal to' a given value, show the rounding step: eg 8.7A (rounded to 9A).
Prefixes: convert units such as kN (kilo-newtons) and mA (milli-amperes) by multiplying or dividing by 1000.
Assumptions: many formulas can only be used with particular assumptions eg a fixed mass of gas or temperature is kept constant etc.
Common-sense: consider whether numerical answers make sense eg a person of mass 5.0 or 500 kg is not likely.
Graphs are often marked for the following features:
Size (more than 50% of the graph paper)
Axis (label quantity and unit; numbers evenly spaced)
Plotting (usually 2 marks for accuracy of points). Mark points with small dots.
Line of best fit (don't join the dots; don't force it through the origin; only draw a straight line if it looks straight; and if it is straight, use a ruler).
Anomalies can be identified as points far from the line of best fit.
Calculating gradient: actually draw the rise-run triangle (make it large). Use measurements of the triangle for the calculation, NOT values from the coordinates. A gradient has a unit.
Proportional quantities: state that a relationship is proportional or linear if A = kB, but not if A = kB + C or if A = kB2. Example: "kinetic energy increases with velocity, but the KE-v graph is non-linear (KE is prop. to v squared)".
Questions about experimental skills
Method: describe all the steps in the right order.
Quantities: give the number and unit (in a table, unit is in the heading).
Repeat readings. The reasons for this are:
make the result more reliable (gives the same result each time);
to find a mean value;
to spot anomalies.
Scales: read them with your eye level with the reading (avoid parallax error).
Zero error: make sure the ruler or meter starts at zero.
Apparatus: learn the names eg measuring cylinder; ray box; ticker-timer; air-track; stand and clamp etc
Examples of Safety precautions
Weights must not fall on toes.
Hot objects must be carried with insulating handles.
Fasten clamp stands to the bench.
Protect eyes from stretched wires; liquids; flying objects.
Lab-coats protect skin and clothes from chemicals and hot materials.
Electricity supplies should be low voltage.
Mop up water if it is spilled.
Radioactive materials must be stored inside lead containers and handled with forceps.
Avoid damage to apparatus (don't exceed limits for elasticity/ current/ temperature/ force etc).
Variables
Independent variable is the one which you choose to change. You can make decisions about the range and number of values. It should be the leftmost column in a table and the horizontal axis on a graph.
Dependent variable is the one which you measure. This is the variable you average when there are repetitions.
Controlled variables are the ones you keep constant to ensure a fair test.
Evaluating conclusions
Precision - this means how many significant figures are used in a measurement. (eg 0.25s has a precision of 0.01s). It can be useful to estimate the precision as a percentage of the reading (eg here it is 4%)
Accuracy - this means how close to the true value the result is.
Reliability - whether a result can be repeated.
Improvements
Reaction time - this can adversely affect measurements of time (add 0.1s). To reduce it, use electronic timing or measurelonger times.
For oscillations, measure several and divide to find time period which will reduce effect of reaction time.
To improve precision you can use a scale with smaller divisions.
Repeat measurement (consider if it is appropriate in each situation).
Does the question require improvement in the method (same apparatus used differently) or equipment (same method, different instruments)?
Explanations
When explaining, give reasons.
Use labelled diagrams if it helps you to explain something.
Mention all of the relevant physics vocabulary.
When explaining a quantity, consider the relevant formulas: eg pressure depends force exerted on an area.
In questions about kinetic theory, talk about particles.
Diagrams
Use a ruler and pencil. Don't rush. Draw large and clearly.
For magnetic fields, the lines must show the direction, form complete loops and NEVER cross nor touch.
In light diagrams, draw the normal and arrows on the rays. Light travels into the eye.
In electric circuits, show conventional current.
so I planned to do something for u all <3
Here r some important formulas for physics paper :
Density = mass/volume
Speed = distance/time
Acceleration = Change in velocity (v-u)/time
Force = mass x acceleration
Weight = mass x g (10 m/s2) OR (10 N/kg)
Moment of force = force x perpendicular distance from a point
Load = spring constant x extension
Pressure = force/area
Pressure in liquid = density x g x height
Compressing gases ( Pressure 1 x Volume 1 = Pressure 2 x Volume 2 )
Work Done = Force x Distance moved
Gravitational Potential Energy = mass x g x height
Kinetic energy = 1/2 x mass x velocity2
Energy transferred 1 = mass x specific heat capacity x temperature change
Energy transferred 2 = mass x specific latent heat
Power = work done/time = energy transferred/time
Efficiency = useful work done/total energy input
Waves = frequency x wavelength
Frequency = 1/period (time)
Refractive index = sin of incidence angle/ sine of refracted angle
Total Internal reflection (sin of critical angle) = 1/reflective index
Charge = current x time
Resistance = Voltage / current
Voltage = Current x Resistance
Resistors in series = Resistor 1 + Resistor 2
Resistors in parallel = 1/Resistor 1 + 1/Resistor 2
Electrical Power = Voltage x current
Electrical energy = Power x time OR Voltage x current x time
Transformers = Output Voltage 2/Input Voltage 1 = Output turns 2/Input turns 1
Current of Transformers = Current 1 x Voltage 1 = Current 2 x Voltage 2
u really need to do this
GENERAL RULES FOR DOING PHYSICS EXAM PAPERS
Read all of the parts of a question before answering it.
Pay attention to the number of marks on offer (eg for 3 marks, you must say at least three things).
1 mark questions saying 'State' or 'Recall' require short, simple answers.
Learn all definitions and formulas word-for-word.
Give enough detail in your answers. State the obvious eg a force is a push or a pull.
Show that you can use Physics vocabulary whenever you can.
Note the action words in the question (and answer accordingly): State; Explain; Complete; Describe; Use (the graph); Suggest; Evaluate
Part questions are usually on a single topic eg the answer to part (a) feeds into (b).
Stay aware of the time (1 mark per minute). If you get stuck, move on and return if you have time at the end.
Don't be afraid to physically act out the electromagnetism hand rules in the exam.
Never leave a question blank. If nothing else, write down relevant formulas or definitions.
As you finish a question, quickly re-read your answer to make sure it makes sense.
Don't leave early. Check and re-check your answers.
After the exam, don't waste time discussing your answers. Look ahead to the next paper.
Calculations: always show your working: there are many marks for this even if the answer is wrong.
These are the stages: Formula - Rearrange - Information - Substitute - Calculate - Answer - Unit
Underline: Show your final answer clearly highlighting or underlining.
Significant figures: There are marks for getting this right. Every answer should be given to the correct number of sf (the same sf as the numbers given in the question). eg 5.2*9.8 = 51 (2 sf). It is a good idea to state the sf to show that you know about it.
Equations: if you are asked to write one down, use words not just symbols.
Rounding: if you are asked to show a quantity is 'approximately equal to' a given value, show the rounding step: eg 8.7A (rounded to 9A).
Prefixes: convert units such as kN (kilo-newtons) and mA (milli-amperes) by multiplying or dividing by 1000.
Assumptions: many formulas can only be used with particular assumptions eg a fixed mass of gas or temperature is kept constant etc.
Common-sense: consider whether numerical answers make sense eg a person of mass 5.0 or 500 kg is not likely.
Graphs are often marked for the following features:
Size (more than 50% of the graph paper)
Axis (label quantity and unit; numbers evenly spaced)
Plotting (usually 2 marks for accuracy of points). Mark points with small dots.
Line of best fit (don't join the dots; don't force it through the origin; only draw a straight line if it looks straight; and if it is straight, use a ruler).
Anomalies can be identified as points far from the line of best fit.
Calculating gradient: actually draw the rise-run triangle (make it large). Use measurements of the triangle for the calculation, NOT values from the coordinates. A gradient has a unit.
Proportional quantities: state that a relationship is proportional or linear if A = kB, but not if A = kB + C or if A = kB2. Example: "kinetic energy increases with velocity, but the KE-v graph is non-linear (KE is prop. to v squared)".
Questions about experimental skills
Method: describe all the steps in the right order.
Quantities: give the number and unit (in a table, unit is in the heading).
Repeat readings. The reasons for this are:
make the result more reliable (gives the same result each time);
to find a mean value;
to spot anomalies.
Scales: read them with your eye level with the reading (avoid parallax error).
Zero error: make sure the ruler or meter starts at zero.
Apparatus: learn the names eg measuring cylinder; ray box; ticker-timer; air-track; stand and clamp etc
Examples of Safety precautions
Weights must not fall on toes.
Hot objects must be carried with insulating handles.
Fasten clamp stands to the bench.
Protect eyes from stretched wires; liquids; flying objects.
Lab-coats protect skin and clothes from chemicals and hot materials.
Electricity supplies should be low voltage.
Mop up water if it is spilled.
Radioactive materials must be stored inside lead containers and handled with forceps.
Avoid damage to apparatus (don't exceed limits for elasticity/ current/ temperature/ force etc).
Variables
Independent variable is the one which you choose to change. You can make decisions about the range and number of values. It should be the leftmost column in a table and the horizontal axis on a graph.
Dependent variable is the one which you measure. This is the variable you average when there are repetitions.
Controlled variables are the ones you keep constant to ensure a fair test.
Evaluating conclusions
Precision - this means how many significant figures are used in a measurement. (eg 0.25s has a precision of 0.01s). It can be useful to estimate the precision as a percentage of the reading (eg here it is 4%)
Accuracy - this means how close to the true value the result is.
Reliability - whether a result can be repeated.
Improvements
Reaction time - this can adversely affect measurements of time (add 0.1s). To reduce it, use electronic timing or measurelonger times.
For oscillations, measure several and divide to find time period which will reduce effect of reaction time.
To improve precision you can use a scale with smaller divisions.
Repeat measurement (consider if it is appropriate in each situation).
Does the question require improvement in the method (same apparatus used differently) or equipment (same method, different instruments)?
Explanations
When explaining, give reasons.
Use labelled diagrams if it helps you to explain something.
Mention all of the relevant physics vocabulary.
When explaining a quantity, consider the relevant formulas: eg pressure depends force exerted on an area.
In questions about kinetic theory, talk about particles.
Diagrams
Use a ruler and pencil. Don't rush. Draw large and clearly.
For magnetic fields, the lines must show the direction, form complete loops and NEVER cross nor touch.
In light diagrams, draw the normal and arrows on the rays. Light travels into the eye.
In electric circuits, show conventional current.
- Messages
- 172
- Reaction score
- 71
- Points
- 38
I know how to do it, so I just asked if I was checking the right question since he said explanation (usually an explaining question..).
Thanks.
sound waves are longitudinal. another example might be oscillation in springs.
electromagnetic waves such as infrared, microwaves, light, UV, x-rays, gamma rays, etc are some examples of transverse waves.
- Messages
- 74
- Reaction score
- 24
- Points
- 28
thanks 
- Messages
- 74
- Reaction score
- 24
- Points
- 28
ok...one more question......a motor changes electrical energy to kinetic or kinetic to electrical????
- Messages
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- Reaction score
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- 28
electrical to ke
- Messages
- 74
- Reaction score
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- Points
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k..thnx
a d.c. motor changes electrical energy to kinetic energy but an a.c generator changes kinetic energy to electrical energy
- Messages
- 74
- Reaction score
- 24
- Points
- 28
thankuu
- Messages
- 74
- Reaction score
- 24
- Points
- 28
can sm1 plz explain dz question:
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_31.pdf
last question part b
http://www.xtremepapers.com/papers/CIE/Cambridge IGCSE/Physics (0625)/0625_s10_qp_31.pdf
last question part b
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Kinetic to electrical
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- Reaction score
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I think that's only if one medium is air; the proper one would be Snell's law, I think.
n1 x sin 01 (theta) = n2 x sin 02 (theta)
- Messages
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- Reaction score
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Who cares?
Just convert it!
In Rarer to Denser = Sin i / Sin r (Air to Glass)
In Denser to Rarer = Sin r / Sin i (Glass to Air)
But they might ask for, say, Glass to water...what then?
- Messages
- 172
- Reaction score
- 71
- Points
- 38
Anyways one of them is rarer than the otherBut they might ask for, say, Glass to water...what then?
Glass is more denser than water.
So Denser to Rarer ... Sin r / Sin i.
If they show a light ray coming out of the water and going into the glass and they ask you to find out the angle...you would be royally screwed by the paperAnyways one of them is rarer than the other
Glass is more denser than water.
So Denser to Rarer ... Sin r / Sin i.
Since that's only for air and another medium...sin r / sin i does not apply in this case