1. Change in Internal E of the system = -(Work done by the system)
2. Torque measures the force applied on a body along a rotation
2.1. Torque = Force*(Displacement from chosen pivot point)*(radius)r*sin(angle between displacement & force)
3. Rotating bodies
3.1. When the net torque on a system is zero, the angular momentum is conserved, that is, it stays constant.
3.2. Angular Momentum (L) = Inertia * (Angular Velocity)
3.3. Inertia describes the distribution of mass High inertia = sparse, Low inertia = concentrated masses
3.3.1. I= Σmr^2 (Moments of Inertia)
3.3.2. Sigma = (Sphere = 2/5) (Cylinder = 1/2) (Rod = 1/12)
3.3.3. This definition of mass moment of inertia needs to be more precise (Boomer)
3.4. Suvat rules still applied
3.4.1. Rotational KE = 1/2 Iω^2
4. Thermodynamics (Khang)
4.1. ΔU is the change in internal energy
4.1.1. ΔU > 0 means the internal energy of the gas increases
4.1.2. ΔU < 0 means the internal energy of the gas decreases
4.2. First Law
4.2.1. An amount of heat Q given to a gas will increase the internal energy of the gas and/or will do work by expanding the gas
4.2.1.1. Q > 0 means heat is supplied to the gas
4.2.1.2. Q < 0 means heat is removed from the gas
4.2.2. Q = ΔU + W
4.2.2.1. W is the work done.
4.2.2.1.1. W > 0 means that work is done by the gas as it expands
4.2.2.1.2. W < 0 means that work is done on the gas by compressing it.
4.3. Second Law - Peter
4.3.1. In any cyclic process, the entropy will either increase or remain the same.
4.3.2. Energy will not flow spontaneously from a low temperature object to a higher temperature object, precluding the perfect refrigerator.
4.3.3. This suggests that it is not possible for heat to flow from a colder body to a warmer body without any work having been done to accomplish this flow.
4.3.4. ΔS = Q/T
4.3.4.1. ΔS is the change in entropy of the system
4.3.4.2. Q is a quantity of heat given to or removed from a system
4.3.4.3. Temperature inside a system T (in kelvin)
4.3.4.4. The unit of entropy is J K−1
4.3.4.4.1. Entropy is the measure of disorder
4.3.4.5. Universe's entropy is never decreasing
4.4. Cyclic processes and pV diagrams
4.4.1. Imagine the cyclic cycle yourself. Peace
4.4.2. Stage 1: Isobaric, Stage 2: Isovolumetric, Stage 3: Isothermal, Stage 4: Isovolumetric
4.4.3. Isobaric
4.4.3.1. An isobaric process is one in which the pressure of the system is constant.
4.4.3.2. The heat energy added to the system does work and increases the internal energy of the system.
4.4.4. Isovolumetric/ Isochoric
4.4.4.1. An isochoric or isovolumetric process is one in which the volume of the system does not change unless there is work done on or by the system.
4.4.4.2. If there is no work done on or by the system then the first law of thermodynamics becomes Q=ΔU
4.4.5. Isothermal
4.4.5.1. An isothermal process is one in which the temperature of the system is constant.
4.4.5.2. It is possible to compress gas with a piston slowly so that the temperature of the gas itself does not change.
4.4.5.3. The process is done slowly to allow the heat to transfer to the surroundings.
4.4.5.4. If there is no phase change the lack of temperature change implies that there is no change in the internal energy of the gas or system. Thus we can write the first law of thermodynamics as: Q=ΔW
4.4.6. Adiabatic
4.4.6.1. No heat enters or leave the system
5. Damped and Forced Oscillations
5.1. Damping (Hyojun)
5.1.1. The loss of energy in an oscillating system
5.1.2. Q factor: the number of the oscillations that a system will perform before it dies out
6. Fluids (HL) - Bibi
6.1. Pressure
6.1.1. Pascal's principle: pressure is transmitted to all parts of an incompressible fluid ==> p1=p2
6.2. Archimides' principle
6.2.1. Body in a fluid experiences buoyant force = weight of displaced fluid = rho * g * V
6.3. Bernoulli equation
6.3.1. Bernoulli equation: static pressure + dynamic pressure + elevational pressure = constant
6.4. Continuity equation
6.4.1. A1* v1 = A2 * v2, A=area of tube, v = velocity
6.5. Stokes' law
6.5.1. Fdrag = 6pi*viscosity*r*v
6.6. Turbulence
6.6.1. R > 2100
6.6.2. R = vr(density)/(viscosity)
6.7. ideal fluid
6.7.1. steady, non-viscous, incompressible