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A Bright Idea: AS Level Physics: Waves

Sound waves.

Primary seismic waves (P-waves).

AS Level Physics

Difference between pressure at surface of liquid and pressure at a certain depth h in a fluid, that has a density, that exists within a certain g

AS Level Physics

<p class="MsoNormal" style="font-size: 18.72px; margin-left: 72pt; text-indent: -72pt;"><span lang="EN-US">The extension of a body (e) is proportional to the applied load (F) provided the proportionality limit is not exceeded<o:p></o:p></span></p><p class="MsoNormal" style="font-size: 18.72px; margin-left: 72pt; text-indent: -72pt;"><span lang="EN-US"> F IS DIRECTLY PROPORTIONAL TO e<o:p></o:p></span></p><p class="MsoNormal" style="font-size: 18.72px; margin-left: 72pt;"><span lang="EN-US">F EQUALS K e </span></p>

AS Level Physics

The extension of a body (e) is proportional to the applied load (F) provided the proportionality limit is not exceeded. F IS DIRECTLY PROPORTIONAL TO e.
F EQUALS K e.

Spring constant = gradient of force-extension graph.

</span></p>

A Bright Idea: AS Level Physics: Motion

The difference between the two quantities.

AS Level Physics

Rotate the hinged arm

AS Level Physics

<h2>
</h2>

<p class="MsoNormal"><span lang="EN-US">Combine the
following equations:<o:p></o:p></span></p>

<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><!--if !supportLists--><span lang="EN-US" style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:
Symbol;mso-ansi-language:EN-US">·<span style="font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: &quot;Times New Roman&quot;;">
</span></span><!--endif--><span lang="EN-US">Work
(W) EQUALS Average force (1/2F) X Extension (e)<o:p></o:p></span></p>

<p class="MsoNormal"><span lang="EN-US">(The force
that is required to extend the object increases in a linear way from zero to
the maximum force, THEREFORE Average force EQUALS 1/2F)<o:p></o:p></span></p>

<p class="MsoListParagraph" style="text-indent:-18.0pt;mso-list:l0 level1 lfo1"><!--if !supportLists--><span lang="EN-US" style="font-family:Symbol;mso-fareast-font-family:Symbol;mso-bidi-font-family:
Symbol;mso-ansi-language:EN-US">·<span style="font-variant-numeric: normal; font-variant-east-asian: normal; font-stretch: normal; font-size: 7pt; line-height: normal; font-family: &quot;Times New Roman&quot;;">
</span></span><!--endif--><span lang="EN-US">F=ke<o:p></o:p></span></p>

<p class="MsoNormal" style="margin-left:180.0pt;text-indent:-180.0pt"><span lang="EN-US">Strain energy Work EQUALS 1/2ke^2 THEREFORE Is represented as the area under
the line of the graph of load (y axis) against extension (x axis) <o:p></o:p></span></p>

AS Level Physics

Combine the
following equations:

Work
(W) EQUALS Average force (1/2F) X Extension (e)
The force that is required to extend the object increases in a linear way from zero to
the maximum force, THEREFORE Average force EQUALS 1/2F

Strain energy
Work EQUALS 1/2ke^2 THEREFORE Is represented as the area under
the line of the graph of load (y axis) against extension (x axis)

AS Level Physics

Total v = y component of v + x component of v
Total s = y component of s + x component of s
Remember: v and s are vector quantities, so use Pythagoras to add them together.

AS Level Physics

Calculate change in momentum (impulse of force) logically. F=F(delta)t/(delta)t

A Bright Idea: AS Level Physics: Motion

1) Understand the situation
2) Note the quantities you need to find
3) Note the quantities you already have
4) Substitute the above into the equation that is composed of the relevant quantities.

Same goes if you need to draw a free-body diagram.

AS Level Physics

Spring Constant (k)
The proportion of force needed to achieve a given extension for a material. A material with a larger spring constant requires a larger force to achieve a given extension, and the inverse is also true.
The constant Force per extension for a particular material, that would enable us to find the extension if we know the load and the dimensions of the object. Different specimens of the same object with different shapes will have a different spring constant
Measured in Newton-metres
calculated by Force divided by extension
calculated by the gradient of a force/extension graph



Young Modulus (E)
The proportion of force needed to achieve a given extension for a material. . A material with a larger Young Modulus requires a larger force to achieve a given extension, and the inverse is also true.

The constant stress per strain, for a particular material, that would enable us to find the extension if we know the load and the dimensions of the object, regardless of its shape

Measured in Newton-meters squared OR Pascals

Calculated by:
Stress/Strain



=(Force/Area) TIMES (original Length/extension)


=(Force/extension) TIMES (original Length/Area)


=spring constant TIMES (original Length/Area)


=gradient of Force-extension graph X the other two quantities that affect the Young modulus


=(Young modulus TIMES Area/ original Length) X (original Length/Area)


=(Force TIMES original length)/(Area TIMES extension)

AS Level Physics (Z notes)

Spring Constant (k)
The proportion of force needed to achieve a given extension for a material. A material with a larger spring constant requires a larger force to achieve a given extension, and the inverse is also true.
The constant Force per extension for a particular material, that would enable us to find the extension if we know the load and the dimensions of the object. Different specimens of the same object with different shapes will have a different spring constant
Measured in Newton-metres
calculated by Force divided by extension
calculated by the gradient of a force/extension graph



Young Modulus (E)
The proportion of force needed to achieve a given extension for a material. . A material with a larger Young Modulus requires a larger force to achieve a given extension, and the inverse is also true.

The constant stress per strain, for a particular material, that would enable us to find the extension if we know the load and the dimensions of the object, regardless of its shape

Measured in Newton-meters squared OR Pascals

Calculated by:
Stress/Strain



=(Force/Area) TIMES (original Length/extension)

=(Force TIMES Original length) DIVIDED BY (Area X Extension)

=(Force/extension) TIMES (original Length/Area)


=spring constant TIMES (original Length/Area)


=gradient of Force-extension graph X original length DIVIDED BY AREA (the other two quantities that affect the Young modulus)

=(Young modulus TIMES Area/ original Length) X (original Length/Area)


=(Force TIMES original length)/(Area TIMES extension)

A Bright Idea: AS Level Physics: Motion

Force per unit cross-sectional area where force acts perpendicularly to area
Symbol: p
Measured in Newtons per square metre

Pressure at a specified depth in a fluid (liquid or gas):
Pressure = Depth X Density X Gravitational field strength.
Pressure increases with the depth below the surface of the fluid (the easiest quantity to vary between depth of fluid, density of fluid and g)
Derivation:

Volume of fluid = Cross-sectional area X Height

Mass of fluid = Density X Volume
= Density X Area X Height

Weight of fluid (force exerted on fluid) = Mass X Gravitational field strength
= Density X Area X Height X Gravitational field strength

Pressure on fluid = Force DIVIDED BY Area
= Density X Area X Height X Gravitational field strength DIVIDED BY Area
= Density X Height X Gravitational field strength.

Difference in pressure between two gases using a manometer:
Difference in height between the water in the two tubes TIMES Density of liquid TIMES g.

The side of the manometer with the lower level of liquid is connected to the gas of a higher pressure.

AS Level Physics

Force per unit area where force acts perpendicularly to area
Symbol: p
Measured in Newtons per square metre
Proportional to the depth below the surface of the liquid (the easiest quantity to vary between depth of liquid, density of liquid and g)

AS Level Physics

For a body to be in rotational equilibrium, the sum of the clockwise moments about any point must equal the sum of the anticlockwise moments about the same point. How to find the sum of the moments in a particular direction: Calculate each moment separately, then add the moments together.

AS Level Physics

Properties:

Transfer energy along the direction of wave propagation without the movement of matter.
Amplitude along the wave can be constant, or it can be changed, but there is naturally no changing pattern of amplitudes.
No phase change occurs.

AS Level Physics (Z notes)

A) In the absence of air resistance:

1) Horizontal component moves with a constant velocity

THEREFORE
final velocity = initial velocity in the kinematic equations
acceleration = 0

2) Vertical component moves with a constant acceleration

THEREFORE
initial velocity = 0 in the kinematic equations

3) Use Pythagoras’ theorem to combine the two components to calculate the required quantity

B) In the presence of air resistance:

1) Horizontal motion: Velocity decreases to 0

2) Vertical motion: Acceleration decreases to 0

AS Level Physics

Can be:
Reflected
Refracted
Diffracted

Can:
Produce interference patterns

How these properties can be demonstrated:
Using a ripple tank, as the motor turns, the wooden bar or small dipper vibrates, creating ripples on the surface of the water that are lit by a light FROM ABOVE. The waves cast shadows on a viewing screen LYING UNDERNEATH THE WAVES. The shadows correspond to a particular point on the wave, and are called wavefronts

AS Level Physics (Z notes)

Substitute for another variable (come on!)

AS Level Physics

When waves hit a plane surface and change direction

Example: When straight waves hit a curved barrier, they could be made to converge, and then diverge again.

AS Level Physics

When the depth of the medium changes. If the depth of the medium decreases, the waves will slow down by: Wavelength decreases, but frequency (number of waves passing a point per second remains the same).

Why this makes sense:

Mathematically: Speed EQUALS Wavelength TIMES Frequency
THEREFORE, if wavelength decreases, but frequency remains the same, speed will decrease.

Logically: If the waves are travelling slower, but the same number of waves need to pass a point per second, the waves need to be shorter, hence the shorter wavelength to maintain the same frequency

AS Level Physics

When a body has no tendency to change its speed of motion

AS Level Physics (Z notes)

Note: Uncertainty is recorded to only 1 significant figure.

Calculated answer from measured quantities:

Number of decimal places in uncertainty = Number of decimal places in answer.

Number of significant figures in measured quantities = (OR 1 more of, but never less of) Number of significant figures answer.

AS Level Physics (Z notes)

They may not take pure numbers into consideration.

Pure numbers: Infinitely accurate numbers that have no unit

AS Level Physics (Z notes)

Textbook definitions:

Average speed:
Distance moved by a particle divided by total time taken.

Average velocity:
Change in displacement of a particle divided by total time taken. Not displacement of a particle in unit time.
Derivation:
We measure the displacement of a particle from the position it was at when we first started counting.
Philosophical note:
The earlier you check, the greater the change that you will see. So don’t just come and judge when you have no idea how far we have come.

AS Level Physics (Z notes)

The potential energy stored in or the work done by an object when it is elastically deformed

Measured in joules

Calculated by:
Work = 1/2 X spring constant X extension squared
Derivation:
Original equation:
Work = Force X extension

Think logically about force:
Force increases from 0 to maximum value THEREFORE Average force = 1/2 maximum force

Substitute into original equation:
Work = 1/2 maximum force X extension

Use force:
Force = spring constant X extension

Substitute into equation:
Work = 1/2 X spring constant X extension squared

AS Level Physics (Z notes)

Fractional increase in the original length of a material

Measured in no units (units of length cancel each other out)

Calculated by
Extension DIVIDED BY Original length

AS Level Physics (Z notes)

Force applied per cross-sectional area of material

Measured in newtons per square metre OR pascals

Calculated by: Force DIVIDED BY Cross-sectional area

NB! When calculating strain from a graph of force to extension at a given extension, use the exact force at the exact extension (strain = force DIVIDED BY cross-sectional area), not average force (strain = half force DIVIDED BY cross-sectional area).

AS Level Physics (Z notes)

Pipette/ burette: 0.05 squared centimetres

Mercury-in-glass thermometer: 1 degree Celsius

Thermocouple: 0.5 degrees Celsius

Voltmeter: 0.01 volts

Ammeter: 0.01 amps

AS Level Physics (Z notes)

In ascending order of wavelengths:

Gamma rays: 10 TO THE POWER OF -16 metres TO 10 TO THE POWER OF -10 and shorter

X rays (overlap): 10 TO THE POWER OF -12 to 10 TO THE POWER OF -9 metres and shorter

UV rays: 10 TO THE POWER OF -9 to 10 TO THE POWER OF -7 metres only

Visible light: 10 TO THE POWER OF -7 to 10 TO THE POWER OF -6 metres only

Philosophical note:
Ultraviolet light:
“It is the visual capacity of their human eyes that decide where I end and you begin. They can’t see me, yet they blame me for causing their death. So therefore they call me invisible.”
#ultraphobia

Infrared light: 10 TO THE POWER OF -6 to 10 TO THE POWER OF -2 metres only

Microwaves (overlap): 10 TO THE POWER OF -3 to 10 TO THE POWER OF -1 metres only

Radio waves: 10 TO THE POWER OF -1 to 10 TO THE POWER OF 4 metres and longer

AS Level Physics (Z notes)

Change in energy, when a force moves a mass through a distance, measures in Joules and calculated by:

1) Work = Average force (1/2F) X Extension (e)
Derivation:
The force that is required to extend the object increases in a linear way from zero to
the maximum force, THEREFORE Average force EQUALS 1/2F

2) Strain energy:
Work = 1/2ke^2
THEREFORE
Is represented as the area under
the line of the graph of load (y axis) against extension (x axis)

To understand what you have just heard, research Young’s modulus of a material.

3) Work = Force X Change in volume of a gas, provided that temperature remains constant, and change in pressure (indicated by motion of piston in a syringe) is so small that it can be assumed to be constant.

4) Work = Voltage X Charge
Derivation:
Work = Force X Displacement in the direction of the force

Electric field strength = Force DIVIDED BY Charge
Force = Electric field strength X Charge

THEREFORE
Work = Electrical field strength X Charge X Displacement

Electrical field strength = Voltage DIVIDED BY Distance between two oppositely charged horizontal parallel plates
Voltage = Electrical field strength X Distance

THEREFORE
Work = Voltage X Charge

AS Level Physics (Z notes)

1) Work in the direction of displacement when it is applied at an angle to the direction of displacement:
W=Fs(cos)theta BECAUSE Cos(theta)=adj/hyp. Do not use opp, not even while trying to calculate it's work, because it does no work whatsoever

2) Work done by a gas:
Work = Force X Change in volume, provided that temperature remains the same, and change in pressure (indicated by movement of piston) is so small that pressure is assumed to be constant (similar to rtp, but constant, not necessarily room)

3) Work done on a charged particle by an electric field between to oppositely charged parallel horizontal metal plates:
Work = Voltage X Charge
Derivation:

Original equation:
Work = Force X Displacement

Use electrical field strength:
Electrical field strength = Force DIVIDED BY Charge
THEREFORE
Force = Electrical field strength X Charge

Substitute into original equation:
Work = Electrical field strength X Charge X Displacement

Recognise:
Voltage = Electrical field strength X Displacement
BECAUSE Electrical field strength = Voltage DIVIDED BY Displacement

THEREFORE
Work = Voltage X Displacement

AS Level Physics

7 X 10 to the power of 10

AS Level Physics

1.1 X 10 to the power of 11

AS Level Physics

4.1 X (10 to the power of 10)

AS Level Physics

5 X (10 to the power of 8)

AS Level Physics

2.1 X (10 to the power of 11) (almost double that of copper)