What are the formulas you need to have memorized for the exam?

[r1111]

I think there are several formulas we need to know for the IB Physics HL exam. I wanted to start a thread on lists of these formulas.

One formula I can think of is Magnetic Field in a solenoid.

B = μ(n/l)I

What are others?

Thanks

[Guest Lognarithm]

w²=k/m for SHM.

Also for CD pit depth calculations, don't forget λ/4n=D where n is the index of refraction

Edited April 14, 2014 by Lognarithm

[r1111]

Another one is the coefficient of volume of expansion from climate change

Also γ = (Δ V)/(V₀Δ Ɵ)

where Δ V is increase in volume

Δ Ɵ is increase in temperature

V0 is original volume

and γ is coefficient of volume of expansion (units are K^-1 or C^-1)

[green5]

x(t)= A cos(wt+b)

v(t)= -wA sin(wt+b)

a(t)= -w^2A cos(wt+b)

from SHM

[khimberleigh]

Capacitance = charge/potential difference (C= q/v)

Mass measured in a mass spectrometer

M=(rqB)/v where r is the radius of the deflection, q is charge, B is magnetic field strength and v is velocity

Radius of a nucleus

r=KQ/V where V is voltage, Q is the charge of the nucleus and K is the Coulomb constant

Gain=Voutput/Vinput (For the Communications option)

Orbital speed v=squareroot(GM/r)

Escape speed v=squareroot(2GM\r)

frequency=1/period (f=1/T)

a= -w^2x for SHM where a is the acceleration, w (omega not 'double u') is the angular velocity and x is displacement. <----- Know this!!! seriously!! One time I was stuck for ages on a question (thankfully not in the real exam) and it was because I needed this formula which isn't in the data booklet but it was in the markscheme.

[Saperthan Sivasuthan]

Oscillations and waves

a= -wx^2

Pendulum T= 2pi Squareroot of length divided by g

Mass spring= 2pi squareroot of m dived by k

Power: Work done divided by time or energy transferred divide by time

Efficiency: power out divided by total power in

Edited April 15, 2014 by Saperthan Sivasuthan

[MitchCampbell]

1) I absolutely recommend you know the simple harmonic motion equation: a = -omega^2 x

This is because the definition is tied to it. A graph of acceleration vs. displacement (a vs x) will give you a straight line, through the origin, with a negative slope. This is all about the definition for SHM: acceleration is proportional to displacement, and opposite in direction to displacement.

Plus, if you know the equation and graph, you can see that omega^2 is the gradient. This is usually the key to solving the tougher questions where they want the frequency. Knowing what omega is gets you that frequency, since omega = 2*pi*f, or 2*pi / T where T is the period

2) Another equation to memorize is Power = energy / time = work / time.

This is so important! This saves you on those paper 2 questions where you mix electric and mechanical energy, or also thermal. So the units of power are Joules/sec, which is otherwise known as Watt. So important. Also comes up to explain power in stars (topic 8) plus in astrophysics (Option E), since the power of a star is also known as luminosity.

....

Those are the main two I would recommend you memorize. Others are nice to know, these two above are need to know. At least that's what I teach my own students at my courses.

Hope that helps!

Cheers,

Mitch