Friday
October 21, 2016

# Posts by Elena

Total # Posts: 4,384

Physics (Stress & Strain)
σ= F/A A=1•2.5=2.5 cm²=2.5•10⁻⁴m² σ= 150000/2.5•10⁻⁴=6•10⁸ N/m². Strain is defined as "deformation of a solid due to stress" and can be expressed as ε= σ/E, where E= Young’s ...
June 24, 2013

Physic (Stress & Strain)
L=1.9 m, A= 11 cm²= 11•10⁻⁴m² F=5450 N ΔL = 2.42 mm =2.42•10⁻³ m Stress σ= F/A = 5450/11•10⁻⁴=4.95•10⁶ N/m²= =4.95 MPa Strain ε = ΔL/L= 2.42•10⁻³/1.9 =1.27•10&#...
June 24, 2013

physics
PE=mgh
June 24, 2013

physics
http://gmanacheril.com/PHY2048/Text%20Materials/Lesson%204.4%20Conditions%20of%20Equilibrium.pdf Example #2
June 24, 2013

Physics
P₁₀₀>P₂₅ => U²/R₁₀₀ > U²/R₂₅. Since U = const => R₂₅>R₁₀₀
June 24, 2013

Physics
50/km/h=13.9 m/s m•a=N•sinα 0=N•cosα - m•g m•v²/R=N•sinα = m•g•sin α/cos α =m•g•tan α tan α = v²/gR =13.9²/9.8•59.9=0.329 α = tan⁻¹=18.19⁰
June 24, 2013

physics
a=(F-R)/m = (4500-1500)/2000=1.5 m/s^2
June 24, 2013

physics
Mv₁=mu+Mv₂ u = M(v₁-v₂)/m = = 208(27.9-20.1)/45.9 = =35.3 m/s
June 24, 2013

Physics
Work =power x time
June 23, 2013

physics
v(vert) = sqrt (2gh) = =sqrt(2•9.8•0.8)=3.96 m/s
June 23, 2013

physics
d=sqrt{(8-6)²+5²}= 5.4 m
June 23, 2013

physics
n=R/A A=R/n = 0.6/1.31=0.458 m http://www.saburchill.com/physics/chapters3/0004.html
June 23, 2013

Physics
E=F/q=0.032/0.003=10.67 V/m, E= - grad φ E=Δφ/Δx= Δφ/d => Δφ=Ed= 10.67•0.04=0.427 V. ΔPE = - Work of electric field= =-q•Δφ=-0.003•0.427= -1.28•10⁻³ J. Δφ=V. C=εε₀...
June 20, 2013

Physics
F=eE=1.6•10⁻¹⁹•2805 = 4.5•10⁻¹⁶ N
June 20, 2013

Physics
ℰ=Δφ=1378 V mv²/2=qΔφ v=sqrt(2qΔφ/m)=…
June 20, 2013

Physics
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F₁₂ =G•m₁•m₂/y²= ... F₃₂ =G•m₃•m₂/x²= ... F=sqrt(F₃₂²+F₁₂²)=... φ is the ...
June 20, 2013

physics
Average speed = =Total distance/ total time = = 2s/{t₁ +t₂} = = 2s/{s/v₁) +(s/v₂)} = =2v₁v₂/(v₁+v₂) = =2•30•45/(30+45) = 36 km/h
June 20, 2013

Physics (Intro)
f=ω/2π =sqrt(k/m)/ 2π f=N/t=20/5=4 Hz
June 19, 2013

physics
C=εε₀A/d ε=1 ε₀=8.85 •10⁻¹² F/m A=1•1=1 cm²=1•10⁻⁴ m² C=q/U=q/Ed ε₀A/d= q/Ed q=ε₀AE=8.85 •10⁻¹²•1•10⁻⁴•1•10⁶= =...
June 19, 2013

science
c) Pascal/s law
June 19, 2013

science
a) Uranium
June 19, 2013

science
d) Gold
June 19, 2013

science
mv=(m+M)u u=mv/(m+M) = 4•10/(4+40) = 0.9 m/s d) 1 m/s
June 19, 2013

science
a) AgNO3
June 19, 2013

science
T=0⁰C = 273 K, p= 1.01325•10⁵ Pa, M=(12+16+16) •10³ = 40•10³ kg/mol. V=mRT/Mp= = 0.004•8.31•273/44•10⁻³•1.01325•10⁵= =0.00204 m³= 2.04 L
June 19, 2013

Physics
W = m•g =G•m•M/R² g= G•M/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10⁶ m.
June 18, 2013

physics
PE=KE+PE₁ mgH = mv²/2 + mgR v²= 2g(H-R) at point A N=mv²/R =2mg(H-R)/R= =2•4.3 •10⁻³•9.8•(0.8-0.31)/0.31 = = 0.133 N
June 18, 2013

Physics
Δh= 13•4.47 m ΔPE =mgΔh = 86.9•9.8•13•4.47= =49487.6 J
June 18, 2013

physics
F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg²,
June 18, 2013

physics
υ = 1.5 mol p= 3 atm = 303975 Pa V=7 L = 0.007 m³ R=8.31 J/mol•K T=? pV= υRT T=pV/υR= =303975•0.007/1.5•8.31=170 K
June 18, 2013

physics
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10⁶ m. r = 850000 m ma=F mv²/(R+r)= G•m•M /(R+r)² v=sqrt{G•M /(R+r...
June 18, 2013

physics
Wavelength = speed/frequency
June 18, 2013

physics
I=q/t q=Ne t=2πR/v I=Nev/2πR= =10¹¹•1.6•10⁻¹⁹•3•10⁸/2π•300 = =0.0025 A
June 18, 2013

physics
v=v₀-gt v=0 t=v₀/g=14/10=1.4 s
June 17, 2013

physics
λ= 630•10⁻⁹ m, d= ? μm = ? •10⁻⁶ m L=4 m k=1 x=? d•sin φ =k•λ sin φ=k•λ/d φ=sin⁻¹(k•λ/d) tan φ= x/L x=L•tan φ
June 17, 2013

Physics
s=v²/2a
June 17, 2013

physics
H-h= gt²/2 t=sqrt{2(H-h)/g} = =sqrt{2(51.5-12.9)/9.8}=2.8 s. v=gt =9.8•2.8=27.44 m/s h₁=12.9 – 1.6 =11.3 m h₁=vt₁+gt₁²/2 gt₁² + vt₁-h₁= 0, t₁² + 27.44t₁- 11.3 = 0, t₁² + 2.8t₁...
June 17, 2013

Physics
Δh=H-h= gt²/2 t=sqrt(2•Δh/g)= =sqrt{2• (3520-1760)/9.8}=18.95 s. s=vt=10•18.95=189.5 m
June 14, 2013

Physics
t=s/v=2300/320=7.1875 h
June 14, 2013

Physics
initial position d₀=0, The maximum height at the motion with initial velocity v₀=20 m/s is H=v₀²/2g=20²/2•9.8 = 20.4 m (!!!) H=v₀t-gt²/2, v(fin)= v₀ -gt, v(fin)=0, => 0= v₀ -gt => v₀ =gt, H=gt²-gt²/2...
June 14, 2013

Physics
Electric field on the axis of the ring at the distance ‘x’ from the center of it is E = k xq/{sqrt(R²+x²)}³ k=1/4πε₀ The test charge is in equilibrium => E₁=E₂ k x₁q₁/{sqrt(R²+x₁²)}³= =k x...
June 13, 2013

physical science
Buoyant force=Weight ρ•V₁•g = Weight V₁=x•y•z₁ ρ•x•y•z₁•g = Weight z₁=Weight/ ρ•x•y•g = =445/1000•4•3•9.8=0.0038 m =3.8 mm
June 13, 2013

physics
The second law for rotation M=Iα => α=M/I M₁/I₁=M₀/I₀ => M₁/M₀=I₁/I₀ I₁ = I₀ => M₁ = M₀ F₁x₁=F₀x₀ F₁/F₀=x₀/x₁=x₀/2x₀ =1/2
June 13, 2013

Physics
The reflectivity R represents the fraction of the incident light that is reflected at the interface R=I/I₀, where I₀ and I are the incident and reflected beams intensities respectively. If the light is normal (or perpendicular) to the interface, then R={(n₂-n...
June 13, 2013

physics
tangent to the path
June 12, 2013

Physics
Suppose that the bullet hits the aim at the upward motion, then h= v₀₁•sinα•t - gt²/2 = v₀₂•sinβ•t - gt²/2, v₀₁•sinα = v₀₂•sinβ , sinβ= v₀₁•sin&#...
June 9, 2013

physics
http://web.mit.edu/8.02t/www/materials/StudyGuide/guide02.pdf page21
June 8, 2013

Physics
n=2.7 rev/s => ω=2πn=2•3.14•2.7 ≈17 rad/s ma=F(fr) mω²R=μmg μ=ω²R/g =17²•0.026/9.8 =0.77
June 8, 2013

physics
F=ma F=eE ma = eE a=eE/m= 1.6•10⁻¹⁹•10³/9.1•10⁻³¹= =1.76•10¹⁴ m/s² s=v₀²/2a = v₀²m/2eE= =(5•10⁶)²•9.1•10⁻³¹/2•1.6•10⁻¹...
June 8, 2013

Physics
under the action of a torque the dipole aspires to be established along the field
June 8, 2013

Physics
under the action of a torque the dipole aspires to be established along the field
June 8, 2013

Physics
v₀=110 km/h=30.6 m/s s=v₀t-at²/2, a=2(v₀t-s)/t²=… v= v₀-at=…
June 7, 2013

Honors Physics- Help PLEASE- Test tmrw
E=Δm•c²= =9.106•10⁻³•1.67•10⁻²⁷•(3•10⁸)²=1.37•10⁻¹²J
June 4, 2013

Physical Science
1A, 2B, 3B,D 4A, 5D, 6D, 7A, 8 ??? λ=v/f
June 4, 2013

Physical Science
1C. at a particular instant. 2A. 4 meters 3B. how fast a velocity is changing at a specific instant 4D. all of the above 5A. the amount of time needed to travel the distance. 6D. The train’s acceleration is negative. 7D. by adding the vectors
June 4, 2013

physics
ω=2π/t, v= ωR, R= v/ω=vt/2π= =24•0.1/2π=0.38 m.
June 4, 2013

PHYSICS
σ=F/A=F/πr² ε=ΔL/L Hook’s law for the wire: k ε= σ k= σ/ ε= F L /πr²ΔL E=k•ΔL²/2= F• L•ΔL²/2πr²ΔL= =F•L•ΔL/2πr²=49•5•10⁻...
June 3, 2013

Difracction problem
For CuKα-radiation λ=1.541•10⁻¹⁰ m. From equation sin²θ₁/(h²+k²+l²)₁=sin²θ₂/(h²+k²+l²)₂=…. const, sin²θ₁/1= sin²θ₂/2= sin²θ...
June 2, 2013

Physics 1 College Level
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², mg =GmM/R², g =G M/R²= =6.67•10⁻¹¹•77.89•10²³/(7.9•10⁶)²= =8.32 m/s²
June 1, 2013

Physics 1 College Level
R=sqrt(D²+d²)=sqrt(3204²+1247²)=3438 m The angle between R and D is cos α =D/R =3204/3438 α=21.26⁰ mass of the spaceship m=? mass of asteroid M=? F₁=GmM/R²=… F=2F₁cos α=…
June 1, 2013

physics
Q=cmΔT=1800•7•(70-35)=441000 J
June 1, 2013

physics
F•Δt=Δp=m•Δv= m(v-0) v= F•Δt/m = 80•0.04/0.058=55.17 m/s
June 1, 2013

physics
sinα =F₁/F₂=0.5 α= 30⁰, the angle between the two forces = 90⁰+30⁰=120⁰
June 1, 2013

MIT 2.01x
http://aerostudents.com/files/materialsAndStructures/Hibbeler8thEditionBookSolutions/Chapter%2005.pdf
May 31, 2013

If RT ia the total R then Rt increases
May 31, 2013

tanφ=X(L)/R = 250/125 = 2 φ=tan⁻¹2=63.4⁰
May 31, 2013

Mathematics Ms Sue help
band-pass filter http://www.ibiblio.org/kuphaldt/electricCircuits/AC/AC_8.html
May 31, 2013

f=1/T=1/10⁻³=1000 Hz
May 31, 2013

An open resistor is a resistor with one of the leads not connected.An open resistor can have no current or voltage, and it can have no effect on any circuit. => 35 Ω and 55 Ω are shorted and 100 Ω is open => ℰ=IR =100•10⁻³• 90 = ...
May 31, 2013

W = Watt (unit of power) Resistance: Ohm =Ω => total resistamce R=100 Ω+35 Ω+55 Ω=190 Ω According to Ohm's Law ℰ=IR =100•10⁻³•190 =19 V ≠ 9 V.
May 31, 2013

physics
ma=F mv²/R=qvBsinα circular path = >sinα = 90⁰ q=e= e =1.6•10⁻¹⁹ C, m=9.1•10⁻³¹ kg R=mv/eB = =9.1•10⁻³¹•3•10⁷/1.6•10⁻¹⁹•0.2 = …
May 31, 2013

physics
Q=0.75V²t/R= =0.75•120²•15•3600/144=4050000 J = 4.05 MJ
May 30, 2013

Physics
φ=ω₀t-εt²/2 ω =ω₀-εt ω=0 ω₀=v/r φ=2πN ε =ω₀²/2φ =v²/2r²•2πN= = v²/4πr²N=36²/4•π•0.3²•40=28.6 rad/s²
May 30, 2013

physics
E=mc²
May 29, 2013

physics
E=mc² m=E/ c²
May 29, 2013

physics
β= v/c=0.3c/c=0.3 L=L₀•sqrt{1-β²)=30•sqrt(1-0.3²)=28.6 m
May 29, 2013

physics
t=t₀/sqrt{1-β²)=11/sqrt(1-0.7²) = 15.4 s
May 29, 2013

physics
P=F/A=NW/A N=PA/W = =1.013•10⁵•0.203•0.089/17.8=102.8 ≈103
May 28, 2013

English
These are questions from Stephen King's collection  "different seasons", particularly the novel "Rita Hayworth and the shawshank redemption": 1. From all the appearances the trial against Andy was pretty much "opens & shut". Identify the ...
May 28, 2013

Physics
h=v₀t+gt²/2 gt²+2 v₀t-2h=0 10 t²+3.4t-90 =0 t= {- 3.4±sqrt(11.56+3600)}/20= = { - 3.4 ± 60.1}/20 t = 2.83 s
May 28, 2013

physics
P=W/A= W/4πr², W=4πr²•P= =4•3.14•(6.37•10⁶)²•1.01•10⁵=5.15•10¹⁹ N
May 28, 2013

sqrt =square root, arctan = tan⁻¹ - inverse trigonometric function – (Broken Link Removed)
May 28, 2013

v=sqrt{(pl)²+v(wind)²} = ... α= arctan{ w(pl)/v(wind)}=... north of west
May 28, 2013

Physics ASAP
http://www.physicstutorials.org/home/mechanics/1d-kinematics/projectile-motion?start=1
May 28, 2013

Physics ASAP
t =sqrt(2h/g) s =vt
May 28, 2013

physics
ΔV/V = αΔT, ΔT = ΔV/ α•V= =0.0015V/V•5.1•10⁻⁵= =0.0015 / 5.1•10⁻⁵= 29.4, t=20+29.4 =49.4℃
May 28, 2013

physics
p= m₁v₁-m₂v₂= 1500•20 - 950•26 = = 30000- 24700 =5300 kg•m/s
May 28, 2013

physics
0=m₁v₁cosα + m₂v₂. v₁= - m₂v₂/m₁ cosα= = - 1.25•4/0.60•cos30 = - 9.62 m/s
May 28, 2013

Physics Acceleration
Δp=p₂-(-p₁) = p₂ + p₁ = m(v₂+v₁), F= Δp/Δt=ma , m(v₂+v₁)/Δt = ma, a= (v₂+v₁)/Δt= =(46+38)/1.05•10⁻³=8•10⁴ m/s²
May 26, 2013

physics
mg´=mω²R₂=m4π²R₂/T², g´=4π²R₂/T², mg´= G•m•M/R₂², mg= G•m•M/R₁², mg´/mg = G•m•M•R₁²/R₂²•G•m•M, g´/g...
May 26, 2013

PHySICS
x=kLλ/d λ=xd/kL= =4.2•10⁻³•1.15•10⁻³/3.9•2=6.2•10⁻⁷ m red
May 26, 2013

Physics
F(1x)=F(1)=10 N F(2x)=F(2)cos60=5•0.5=2.5 N F(2y) =F(2)sin60 = 5•0.866= 4.33 N F(3x) =- F(x)=- (10+2.5 )= -12.5 N F(3y) =- F(2y)= - 4.33 N F(3) = sqrt{ F(3x)²+F(3y)²} =13.23 N tan φ = F(3y)/F(3x) =4.33/12.5=0.364 φ = 19.1⁰ (south-west)
May 25, 2013

Physics
s=BC=1 m a) PE=KE₁ mgh = mv₁²/2 v₁=sqrt(2gh)=… b,c) KE₂=PE(spring) mv₂²/2 =kx²/2 v₂=sqrt{ kx²/m} =… KE₁=W(fr)+KE₂ mv₁²/2 = μmgs+ mv₂²/2 μ=(1/mgs)•{ mv₁²...
May 25, 2013

Physics
The circumference of the axel is L=πd, the string wraps around the axel N=s/L= s/ πd. The angle of rotation is φ=2πN=2 πs/ πd=2s/d= =2•80/2=80 rad
May 25, 2013

science
L=vₒ²•sin2α/g= vₒ²•2sinα•cosα/g h= vₒ²•sin²α/2g, h/L = vₒ²•sin²α•g / vₒ²•2sinα•cosα• 2g= =tan α/4=tan45/4=1/4=0.25 h=0.25L=0.25...
May 22, 2013

Physics
h= gt²/2 => t=sqrt{2h/g}, s=vt
May 22, 2013

physics
Q=IVt=(q/t)Vt=qV=eV= =1.6•10⁻¹⁹•9=1.44•10⁻¹⁸J.
May 22, 2013

Physics
http://web.mit.edu/8.02t/www/materials/StudyGuide/guide02.pdf
May 22, 2013

http://m.teachastronomy.com/astropedia/article/Critical-Density
May 21, 2013

In vector form: Δp⃗ =p₂⃗-p₁⃗ =mv₂⃗-mv₁⃗, for magnitudes Δp =p₂-(-p₁) =mv₂+mv₁= 2mv. p=Mu => Mu=2mv The speed of the center of the door is u=2mv/M=2•0.4•35/15 = 1.37 m/s Its ...
May 21, 2013

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