OpenStax University Physics/V1/Formulas (master)

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<section begin=Introduction/>Introduction

metric prefixes
da h k M G T P E Z Y
deca hecto kilo mega giga tera peta exa zetta yotta
1E+01 1E+02 1E+03 1E+06 1E+09 1E+12 1E+15 1E+18 1E+21 1E+24
d c m µ n p f a z y
deci centi milli micro nano pico femto atto zepto yocto
1E-01 1E-02 1E-03 1E-06 1E-09 1E-12 1E-15 1E-18 1E-21 1E-24

<section end=Introduction/>


<section begin=Units_and_Measurement/>1. Units_and_Measurement:  The base SI units are mass: kg (kilogram); length: m (meter); time: s (second). [1]

Percent error is (δA/A)×100% <section end=Units_and_Measurement/>

<section begin=Vectors/>

2. VectorsVector

A=Axi^+Ayj^+Azk^

involves components (Ax,Ay,Az) and [2] unit vectors.[3] ▭ If

A+B=C

, then Ax+Bx=Cx, etc, and vector subtraction is defined by

B=CA

.

▭ The two-dimensional displacement from the origin is r=xi^+yj^. The magnitude is A|A|=Ax2+Ay2. The angle (phase) is θ=tan1(y/x). ▭ Scalar multiplication αA=αAxi^+αAyj^+... ▭ Any vector divided by its magnitude is a unit vector and has unit magnitude: |V^|=1 where V^V/V ▭ Dot product AB=ABcosθ=AxBx+AyBy+... and AA=A2 ▭ Cross product A=B×C Aα=BβCγCγAβ where (α,β,γ) is any cyclic permutation of (x,y,z), i.e., (α,β,γ) represents either (x,y,z) or (y,z,x) or (z,x,y). ▭ Template:Nowrap magnitudes obey A=BCsinθ where θ is the angle between B and C, and A{B,C} by the right hand rule. ▭ Vector identities c(𝐀+𝐁)=c𝐀+c𝐁 ▭ 𝐀+𝐁=𝐁+𝐀 ▭ 𝐀+(𝐁+𝐂)=(𝐀+𝐁)+𝐂 ▭ 𝐀𝐁=𝐁𝐀 ▭ 𝐀×𝐁=𝐁×𝐀 ▭ (𝐀+𝐁)𝐂=𝐀𝐂+𝐁𝐂 [4] <section end=Vectors/>

<section begin=Motion_Along_a_Straight_Line/>3. Motion_Along_a_Straight_Line[5] ▭ Average velocity v¯=Δx/Δtv=dx/dt (instantaneous velocity) ▭ Acceleration a¯=Δv/Δta=dv/dt. ▭ WLOG set Δt=t and Δx=xx0 if ti=0. Then Δv=vv0, and v(t)=0ta(t)dt+v0, x(t)=0tv(t)dt+x0=x0+v¯t[6] ▭ At constant acceleration: v¯=v0+v2,v=v0+at,x=x0+v0t+12at2, v2=v02+2aΔx. ▭ For free fall, replace xy (positive up) and ag, where g = 9.81 m/s2 at Earth's surface). <section end=Motion_Along_a_Straight_Line/>

<section begin=Motion_in_Two_and_Three_Dimensions/>4. Motion_in_Two_and_Three_DimensionsInstantaneous velocity: v(t)=vx(t)i^+vy(t)j^+vz(t)k^=dxdti^+dydtj^+dzdtk^ ▭ v(t)=limΔt0ΔrΔt=limΔt0r(t+Δt)r(t)Δt, where r(t)=x(t)i^+y(t)j^+z(t)k^ ▭ Acceleration a=axi^+ayj^+azk^, where ax(t)=dvx/dt=d2x/dt2. [7] ▭ Uniform circular motion: position r(t), velocity v(t)=dr(t)/dt, and acceleration a(t)=dv(t)/dt: r=Acosωti^+Asinωtj^, v=Aωsinωti^+Aωcosωtj^, a=Aω2cosωti^Aω2sinωtj^. Note that if A=r then |a|=aC=ω2r=v2/r where v|v|=ωr. [8] ▭ Relative motion: [9] vPS=vPS+vSS, [10] <section end=Motion_in_Two_and_Three_Dimensions/>

<section begin=Newton's_Laws_of_Motion/>5. Newton's_Laws_of_Motion[11]ma=dp/dt=Fj, where p=mv is momentum, [12] Fj is the sum of all forces This sum needs only include external forces [13]FAB=FBA.[14]

▭ Weight=w=mg. ▭ normal force[15] |N|=N=mgcosθ[16] ▭ [17]F=kx where k is the spring constant. <section end=Newton's_Laws_of_Motion/>

<section begin=Applications_of_Newton's_Laws/>6. Applications_of_Newton's_LawsfsμsN and fk=μkN: f= friction, μs,k= coefficient of (static,kinetic) friction, N= normal force. ▭ Centripetal forceFc=mv2/r=mrω2 for uniform circular motion. Angular velocity ω is measured in radians per second. [18]▭ Drag equation FD=12CρAv2 where C= Drag coefficient, ρ= mass density, A= area, v= speed. Holds approximately for large Reynold's number[19] <section end=Applications_of_Newton's_Laws/>

<section begin=Work_and_Kinetic_Energy/>7. Work_and_Kinetic_EnergyInfinitesimal work[20] dW=Fdr=|F||dr|cosθ leads to the path integral WAB=ABFdr ▭ Work done from A→B by friction fk|AB|,gravity mg(yByA), and spring 12k(xB2xA2) ▭ Work-energy theorem: [21] Wnet=KBKA where kinetic energy =K=12mv2=p22m. ▭ Power=P=dW/dt=Fv. <section end=Work_and_Kinetic_Energy/>

<section begin=Potential_Energy_and_Conservation_of_Energy/>8. Potential_Energy_and_Conservation_of_EnergyPotential Energy: ΔUAB=UBUA=WAB; PE at r WRT r0 is ΔU=U(r)U(r0) U=mgy+𝒞 (gravitational PE Earth's surface. U=12kx2+𝒞 (ideal spring) ▭ Conservative force: Fconsdr=0. In 2D, F(x,y) is conservative if and only if F=(U/x)i^(U/y)j^Fx/y=Fy/x ▭ Mechanical energy is conserved if no non-conservative forces are present: 0=Wnc,AB=Δ(K+U)AB=ΔEAB <section end=Potential_Energy_and_Conservation_of_Energy/>

<section begin=Linear_Momentum_and_Collisions/>9. Linear_Momentum_and_CollisionsF(t)=dp/dt, where p=mv is momentum. ▭ Impulse-momentum theorem J=FaveΔt=titfFdt=Δp. ▭ For 2 particles in 2D If Fext=0 then j=1Npj=0pf,α=p1,i,α+p2,i,α where (α,β)=(x,y) ▭ Center of mass: rCM=1Mj=1Nmjrj1Mrdm, vCM=ddtrCM, and pCM=j=1Nmjvj=MvCM. ▭ F=ddtpCM=maCM=j=1Nmjaj [22] <section end=Linear_Momentum_and_Collisions/>

<section begin=Fixed-Axis_Rotation/>10. Fixed-Axis_Rotation

θ=s/r is angle in radians,ω=dθ/dt is angular velocity; ▭ vt=ωr=ds/dt is tangential speed. Angular acceleration is α=dω/dt=d2θ/dt2. at=αr=d2s/dt2 is the tangential acceleration. ▭ Constant angular acceleration ω¯=12(ω0+ωf) is average angular velocity. ▭ θf=θ0+ω¯t=θ0+ω0t+12αt2. ▭ ωf=ω0+αt. ωf2=ω02+2αΔθ. ▭ Total acceleration is centripetal plus tangential: a=ac+at. ▭ Rotational kinetic energy is K=12Iω2, where I=jmjrj2r2dm is the Moment of inertia. ▭ parallel axis theorem Iparallelaxis=Icenterofmass+md2 ▭ Restricting ourselves to fixed axis rotation, r is the distance from a fixed axis; the sum of torques, τ=r×F requires only one component, summed as τnet=τj=rjFj=Iα. ▭ Work done by a torque is dW=(τj)dθ. The Work-energy theorem is KBKA=WAB=θAθB(jτj)dθ. ▭ Rotational power =P=τω. <section end=Fixed-Axis_Rotation/>

<section begin=Angular_Momentum/>11. Angular_MomentumCenter of mass (rolling without slip) dCM=rθ, vCM=rω,aMC=Rα=mgsinθ/m+(Icm/r2) ▭ Total angular momentum and net torque: dL/dt=τ =l1+l2+...; l=r×p for a single particle. Ltotal=Iω. ▭ Precession of a top ωP=mrg/(Iω).<section end=Angular_Momentum/>

<section begin=Static_Equilibrium_and_Elasticity/>12. Static_Equilibrium_and_ElasticityEquilibrium Fj=0=τj. Stress = elastic modulus · strain (analogous to Force = k · Δ x ) ▭ (Young's , Bulk , Shear) modulus: (FA=YΔLL0,Δp=BΔVV0,FA=SΔxL0) <section end=Static_Equilibrium_and_Elasticity/>

<section begin=Gravitation/>13. GravitationNewton's law of gravity F12=Gm1m2r2r^12 ▭ Earth's gravity g=GMEr2 ▭ Gravitational PE beyond Earth U=GMEmr ▭ Energy conservation 12mv12GMmr1=12mv22GMmr2 ▭ Escape velocity vesc=2GMEr ▭ Orbital speed vorbit=GMEr ▭ Orbital period T=2πr3GME ▭ Energy in circular orbit E=K+U=GmME2r ▭ Conic section αr=1+ecosθ ▭ Kepler's third lawT2=4π2GMa3 ▭ Schwarzschild radius RS=2GMc2 <section end=Gravitation/>

<section begin=Fluid_Mechanics/>14. Fluid_MechanicsMass density ρ=m/VPressure P=F/APressure vs depth/height (constant density)p=po+ρghdp/dy=ρgAbsolute vs gauge pressure pabs=pg+patmPascal's principle: F/A depends only on depth, not on orientation of A. ▭ Volume flow rate Q=dV/dtContinuity equation ρ1A1v1=ρ2A2v2A1v1=A2v2 if ρ=const. <section end=Fluid_Mechanics/>

<section begin=Oscillations/>15. OscillationsFrequency f, period T and angular frequency ω: fT=1,ωT=2π ▭ Simple harmonic motion x(t)=Acos(ωt+ϕ), v(t)=Aωsin(ωt+ϕ), a(t)=Aω2cos(ωt+ϕ) also models the x-component of uniform circular motion. ▭ For (A,ω) positive: xmax=A,vmax=Aω,amax=Aω2 ▭ Mass-spring ω=2π/T=2πf=k/m; ▭ Energy ETot=12kx2+12mv2=12kA2v=±km(A2x2) ▭ Simple pendulum ωg/L ▭ Physical pendulum τ=MgLsinθMgLθω=mgL/I and L measures from pivot to CM. ▭ Torsional pendulum τ=κθω=I/κ ▭ Damped harmonic oscillator md2xdt2=kxbdxdtx=A0eb2mtcos(ωt+ϕ) where ω=ω02(b2m)2 and ω0=km. ▭ [23]Forced harmonic oscillator (MIT wiki!)] md2xdt2=kxbdxdt+F0sinωtx=Aeb2mtcos(ωt+ϕ) where A=F0m2(ωω0)2+b2ω2. <section end=Oscillations/>

<section begin=Waves/>16. Waves[24] Wave speed] (phase velocity) v=λ/T=λf=ω/k where k=2π/λ is wavenumber. ▭ Wave and pulse speed of a stretched string =FT/μ where FT is tension and μ is linear mass density. ▭ Speed of a compression wave in a fluid v=B/ρ. ▭ Periodic travelling wave y(x,t)=Asin(kxωt) travels in the positive/negative direction. The phase is kxωt and the amplitude is A. ▭ The resultant of two waves with identical amplitude and frequency yR(x,t)=[2Acos(ϕ2)]sin(kxωt+ϕ2) where ϕ is the phase shift. ▭ This wave equation 2y/t2=vw22y/x2 is linear in y=y(x,t) ▭ Power in a tranverse stretched string wave Pave=12μA2ω2v. ▭ Intensity of a plane wave I=P/AP4πr2 in a spherical wave. ▭ Standing wave y(x,t)=Asin(kx)cos(ωt+ϕ) For symmetric boundary conditions λn=2π/kn=2πL n=1,2,3,..., or equivalently f=nf1 where f1=v2L is the fundamental frequency. <section end=Waves/>

<section begin=Sound/>17. SoundPressure and displacement fluctuations in a sound wave P=ΔPmaxsin(kxωt+ϕ) and s=smaxcos(kxωt+ϕ) ▭ Speed of sound in a fluid v=fλ=β/ρ, ▭ in a solid Y/ρ, ▭ in an idal gas γRT/M, ▭ in air 331msTK273K=331ms1+TC273oC ▭ Decreasing intensity spherical wave I2=I1(r1r2)2 ▭ Sound intensity I=PA=(ΔPmax)22ρv ▭  ...level 10log10I/I0 ▭ Resonance tube One end closed: λn=4nL, fn=nv4L, n=1,3,5,... ▭ Both ends open: λn=2nL, fn=nv2L, n=1,2,3,... ▭ Beat frequency fbeat=|f2f1| ▭ (nonrelativisticDoppler effect fO=fsv±vovvs where v is the speed of sound, vs is the velocity of the source, and vo is the velocity of the observer. ▭ Angle of shock wave sinθ=v/vs=1/M where v is the speed of sound, vs is the speed of the source, and M is the Mach number.

I=∫r2dm for a hoop, disk, cylinder, box, plate, rod, and spherical shell or solid can be found from this figure.

<section end=Sound/>

Footnotes

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  1. [http://wiki.ubc.ca/index.php?title=Uncertainty_and_Error&oldid=81540
  2. three orthonormal
  3. ▭ (𝐀+𝐁)×𝐂=𝐀×𝐂+𝐁×𝐂 ▭ 𝐀(𝐁×𝐂)=𝐁(𝐂×𝐀)=(𝐀×𝐁)𝐂▭ 𝐀×(𝐁×𝐂)=(𝐀𝐂)𝐁(𝐀𝐁)𝐂 ▭ (A×B)(𝐂×𝐃)=(𝐀𝐂)(𝐁𝐃)(𝐁𝐂)(𝐀𝐃)
  4. Delta as difference Δx=xfxidx0 in limit of differential calculus.
  5. , where v¯=1t0tv(t)dt is the average velocity.
  6. ▭ Average values: vave=ΔrΔt=r(t2)r(t2)t2t1, and aave=ΔvΔt=v(t2)v(t2)t2t1 ▭ Free fall time of flight Tof=2(v0sinθ0)g, ▭ Trajectory y=(tanθ0)x[g2(v0cosθ0)2]x2, ▭ Range R=v02sin2θ0g
  7. ▭ Tangential and centripetal acceleration a=ac+aT where aT=d|v|/dt.
  8. rPS=rPS+rSS,
  9. vPC=vPA+vAB+vBC, aPS=aPS+aSS
  10. Newton's 2nd Law
  11. m is mass, and
  12. because all internal forces cancel by the 3rd law
  13. The 1st law is that velocity is constant if the net force is zero.
  14. is a component of the contact force by the surface. If the only forces are contact and weight,
  15. where θ is the angle of incline.
  16. Hooke's law
  17. ▭ Ideal angle of banked curve: tanθ=v2/(rg) for curve of radius r banked at angle θ.
  18. =Re=ρvL/η, where η=dynamic viscosity; L= characteristic length. ▭ Stokes's law models a sphere of radius r at small Reynold's number: Fs=6πrηv.
  19. done by force:
  20. The work done on a particle is
  21. ▭ Rocket equation mdv=udmΔv=uln(mf/mi) where u is the gas speed WRT the rocket.
  22. [https://scripts.mit.edu/~srayyan/PERwiki/index.php?title=Module_3_--_Damped_and_Driven_Harmonic_Oscillations&oldid=7055
  23. [http://wiki.ubc.ca/index.php?title=Waves_and_the_Doppler_Effect&oldid=218637

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