Physics Reviews (A level)

So you've read the title, I bet you think this topic will be easy-peasy, right? Wrong! Not that I want to discourage, as it certainly isn't the hardest topic, but as the last paper 1 topic, there is a bit to learn. It basically talks about pendulums and swingy things. 

A large portion of the topic involves oscillations. This term has been discussed before, when discussing transverse and longitudinal waves. An object oscillating describes how it moves back and forth through the equilibrium position. The equilibrium position is basically the natural position, so where, as long as the object isn't in perpetual motion, the object would eventually stop. The displacement from the equilibrium position is always changing, as it increases as the object moves one way to the maximum displacement (the amplitude), then decreases as the object moves back to the equilibrium position, then the same thing happens again in the opposite direction.

In one oscillation cycle, the object travels through the equilibrium position twice and the amplitude twice . Also the normal terminology applies, so a time period is the time for a cycle, and f=1/T.

So for example, a measuring the cycle for a pendulum, from the starting point it would fall down and pass through the equilibrium position (d->0), then oscillate up to the amplitude (d-> Amp), then oscillate back down again through the equilibrium position (d->0), then up again to the Amplitude. It it important to say that it does pass through the starting position, but the cycle isn't finished yet. So after the amplitude is reached, the pendulum falls back down, then when it reaches the starting position the cycle is finished.

In reality, because of air resistance, the oscillations would eventually stop. This would happen gradually so each cycle the amplitude becomes less and less each time. However, in a hypothetical situation where this wasn't the case, so the amplitude was constant each time, we would describe the oscillations as being free vibrations, just to give it a fun name.

Also for a quick note before we move on, the text book says that angular frequency ω of oscillating motion=2πf. Yes, I know, this is the equation for angular velocity in circular motion. However, the textbook says so, so I guess we'll just have to keep that in mind, unless the textbook is going senile, which I hope for all our sakes isn't true.

If you have 2 oscillations going on at the same time, then there will be a phase difference between them. The difference in times will be Δt/t, which in phase difference in radians will be 2πΔt/T

The displacement of SHM starting will be a cos graph, as it starts at max displacement, then goes through the equilibrium (s=0) to the other max displacement. The equation is [data sheet]

Greatest v when s=0

Differentiate that and you get velocity, diff again and acceleration.

a is greatest when s=max, a=0 when s=0.

Definition of SHM:

a is proportional to displacement, and always in the opposite direction

a∝-x

SHM and circualr motion are heavily related

light- oscillating, A decreases

critical- returns to equilib in quickest time 

heavy- slowly returns to equib in 

Periodic force- force applied at regular intervals

forced oscillations- resultant when periodic F

Applied freq- resultant f when periodic 

Natural freq- system oscillates without periodic force

resonance- periodic F acts on object same point each cycle

app=nat= pi/2 max A