Monday
September 22, 2014

Posts by elena


Total # Posts: 4,331

Physics
1. mv²/2=μmgs s=v²/2μg 2. mv²/2=Q=cmΔT ΔT=v²/2c (c=129000 J/kg•C) 3. Q=cmΔT= mv²/2 Q1= cmΔT1=cm•2=… ΔQ=Q1-Q= cm•2- mv²/2 = …
January 28, 2013

physics
1/do +1/di =1/f f= - 0.6 m (for diverging lens), do= 1.5 m 1/di=-1/do+1/f=-(1/1.5+1/0.6)=2.33 di= - 0.43 m (‘-‘ as the image is in front of the lens) Magnification M= - di/do=0.43/1.5=0.287 h=M•H=0.287•10=2.87 cm
January 28, 2013

physics
E=mgh1-mgh2=mg(h1-h2)= =0.1•9.8(1-0.8)=0.78 J
January 28, 2013

Physics
α=180-61.2=118.8° Cosine Law d=sqrt{20.2²+31.3²-2•20.2•31.3•cos118.8°} = =44,7 km Sine Law 31.3/sinθ=44.7/sin118.8° sinθ=31.3 •sin118.8°/44.7=0.61 θ= 37.9°
January 28, 2013

Physics
g=GM/R² gʹ=GM/(R+H)²= GM/(R+H)²= GM/(4R)²= GM/16R² {GM/R²}/{GM/16R²}=16 =9.8/gʹ gʹ=g/16=9.8 /16=0.61 m/s²
January 28, 2013

Physical Science
Q=λm=335000•0.1=33500 J
January 28, 2013

Physics
the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², F=6.673•10⁻⁹ N R=10 m F =G•m₁•m₂/R²= G•4m•m/R²= G•4m²/R² m=sqrt{F R²/4G)=…
January 28, 2013

Physics
I=q/t => q=It=0.74•10⁻³•4•3600=10.66 C, N=q/e=10.66/1.6•10⁻¹⁹=6.66•10¹⁹
January 28, 2013

mechanics of materials
D=150 mm =0.15 m d= 120 mm = 0.12 m T=40 kN•m = 40000 N•m. J=π(D²-d²)/32 =... T/J=Gθ/L=τ(min)/r, τ(min) = Tr/J=Td/2J=... T/J=Gθ/L=τ(max)/R, τ(max) = TR/J=TD/2J=...
January 28, 2013

mechanics of materials
E=210 GPa (210 MPa isn’t correct) t=6 mm=6•10⁻³m R=6 m Maximum bending stress is σ(max) = E•t/2R=210•10⁹•6•10⁻³/2•6=105•10⁶ N/m²
January 28, 2013

mechanics of materials
τ=T/A=400000/25•10⁻⁴=1.6•10⁸ N/m²
January 28, 2013

mechanical properties of materials
σ=Eε, W/A= Eε, ε=W/AE, Energy=E ε²/2 = E W²/2A²E²= = W²/2A²E= =(30000)²/2•(1200•10⁻⁶)²•210•10⁹= =1.49•10³ J.
January 28, 2013

mechanical properties of materials
σ=Eε σ=F/A=4F/πd² ε= ΔL/L 4F/πd²=ΔL/L d=sqrt{4FL/πEΔL} = =sqrt{4•650•0.17/π•210•10⁹•0.015•10⁻³}= =6.68•10⁻³ m
January 28, 2013

Physics
ε=dÔ/dt = d(NBAcosωt)/dt = = - NBAω sinωt, ε(max) = NBAω => ω=ε(max)/ NBA =45/50•0.4•0.35 =6.43 rad/s
January 28, 2013

Science; Solar System
http://www.universetoday.com/34577/inner-and-outer-planets/ http://en.wikipedia.org/wiki/Sun
January 28, 2013

physical science
T=3000 N 1. T(x)=Tcosα = ..... 2. T(y) = Tsinα = …..
January 28, 2013

Physics
a=mv²/R=? h=gt²/2 t=sqrt(2h/g) = sqrt(2•1.83/9.8)=0.61 s. L=v•t = > v=L/t=2.39/0.61=3.92 m/s a= mv²/R= m•(3.92)²/ 0.486 =… You need mass ‘m’
January 28, 2013

physics
υ=2.2 mol, N₀=6.022•10²³ mol⁻¹, k=1.38•10⁻²³ J/K KE(ave) = υ•N₀•3kT/2 KE(bullet)=mv²/2 υ• N₀•3kT/2= mv²/2 T= mv²/3k• υ• N₀= =7.7•10&#...
January 28, 2013

physics
Fig.1: path difference Δ₁=0, since distances between each loudspeaker and point O are L For constructive interference Δ₁=2kλ/2=kλ (k(min)=0) => Δ₁=0. Fig.2: path difference Δ₂=L√2 – L= L(√2 –1)= 0....
January 28, 2013

math
0.85(0.8x)=0.68x => - 32% 1.25(1.4x)=1.75x = > +75%
January 27, 2013

Physics
h=gt²/2
January 27, 2013

physics
h=1.8 m, H=6 m, v=7 m/s u=? x is the distance of man to lamp post, y is the distance from the tip of the shadow to the lamp post. From the similar triangles H/h = y/(y-x), 6/1.8 = y/(y-x), 6y -6x=1.8y, 4.2 y=6 x, 0.7y=x, d{0.7y}/dt=dx/dt, 0.7(dy/dt)=dx/dt, 0.7u =v, u=v/0.7=7/0...
January 27, 2013

physics
Take the ring of the radius ‘r’ and the width ‘dr’ on the disc. The electric field at the distance ‘x’ from the center of the disc is dE=x•dq/4πε₀• {sqrt(r²+x²)}³, where dq=σ•dA = σ•2&#...
January 27, 2013

Physics
Δφ=2•π•Δx/λ=2•π•0.15/0.65=0.46 π (rad)= =1.45 (rad)
January 27, 2013

Physics
http://ca.answers.yahoo.com/question/index?qid=20120128195228AAtlh44
January 27, 2013

Physics
F=k•q₁•q₂/r² k =9•10⁹ N•m²/C²
January 26, 2013

pHYSICS
R(smaller) =r R(larger) = R in series: 1.99(R+r)=12 . ... ..(1) in parallel: 1/R +1/r=1/R₀ R₀=rR/(R+r) 10.7 R₀=12 10.7•rR/(R+r)=12 …..(2) Multiply (1) by (2) 1.99• (R+r)•10.7•rR/(R=r) =144 r=6.76/R …… (3) From (1) R+r=6.03...
January 26, 2013

math liberal arts
5600/0.4•1.358=10309.3 USD
January 26, 2013

Math
x=x₁+x₂= 1000sin60 =100sin20= =1000(sin60+sin20)= =1000(0.866+0.342)=1208 feet
January 26, 2013

math
M-3=±11 M₁₂=14 M₂ =-8
January 26, 2013

physics
V=V1-V2= πR²h-πr² h=πh(R²-r²) m=ρV=ρπh(R²-r²)
January 26, 2013

Physics
F=qvBsinα F1=q(v/2)(2B)sinα = qvBsinα = 1.2x10^-3 T
January 25, 2013

Physics
The object is at the earth's surface.
January 25, 2013

Physics
F=qvBsinα F1=q(v/2)(2B)sinα = qvBsinα = 1.2x10^-3 T
January 25, 2013

physics
http://en.wikipedia.org/wiki/Thermal_resistance
January 25, 2013

Physics
v = sqrt(TL₀/m)= =sqrt(540•0.9/0.0038) =357.6 m/s. Fundamental frequency f: λ=v/f=2L f=v/ λ=v/2L=357.6/2•0.62 = 288.4 Hz. f1=v/λ₁=v/L=357.6/0.62=576.8 Hz f2=v/λ₂=v/(2L/3)=3 v/2L=865.2 Hz
January 25, 2013

phy
KE(tr) =3kT/2= .... k=1.38•10⁻²³ J/K, T=273+27=300 K.
January 24, 2013

phy
ΔS =ΔQ/T= cmΔT/T = =600•0.5•280/20=4200 J/K
January 24, 2013

phy
ΔQ=ΔU+W ΔU = ΔQ – W = =c•m•ΔT + r•m – p•ΔV= = c•m•ΔT + r•m – p{V- (m/ρ)} = =4190•2•10 +2.26•10⁶•2 – 101325(3.3 – 2/1000) = 4515630 J
January 24, 2013

phy
R=kσT⁴ = 0.92•5.67•10⁻⁸•3000⁴=… W/m² R=P/A => P=AR= A•kσT⁴ = =8•10⁻⁶•0.92•5.67•10⁻⁸•3000⁴= 33.8 W
January 24, 2013

phy
surface tension
January 24, 2013

phy
Q = rm= 2•10⁶•1.5=3•10⁶ J t=Q/P= 3•10⁶/2•10³=1500 s=25 min=0.42 h
January 24, 2013

phy
F₁=kx₁ F₂=kx₂ F₁/F₂=x₁/x₂ x₂=x₁F₂/F₁=…. New length is L+ x₂=…
January 24, 2013

phy
F=kx=k(L-L`) k=F/(L-L`) W=kx²/2= F (L-L`)²/2(L-L`)= F (L-L`)/2.
January 24, 2013

Physics
α=(90-24)+ 37=103⁰ Cosine law: d=sqrt{ 41²+33²-2•41•33•cos103⁰}=58 km Sine law: 33/sinβ=58/sin α sinβ= sin α•33/58=0.554 β=sin⁻¹0.554=33.7⁰ angle=33.7⁰-24⁰=9.7⁰ (north of...
January 24, 2013

science (physics)
Weight = mg m=Weight/g=3920/9.8=... (kg)
January 24, 2013

science (physics)
acceleration due to gravity g= 9.8 m/s^2
January 24, 2013

Physics
q=2.1μC=2.1•10⁻⁶ C, the side of square ia “a” . The potential at the empty corner due to two charges φ=φ₁+φ₂ = kq/a + kq/a= 2kq/a The potential at the empty corner due to three charges φ`=φ₁+φ&#...
January 24, 2013

Physics
mg=17.1 N => mg= kx k=mg/x On the moon mg`=kx₁ x₁=mg`/k =m•1.6•g•x /mg=1.6x=1.6•0.044=0.0704 m
January 24, 2013

Physics
q=2.1μC=2.1•10⁻⁶ C, the side of square ia “a” . The potential at the empty corner due to two charges φ=φ₁+φ₂ = kq/a + kq/a= 2kq/a The potential at the empty corner due to three charges φ`=φ₁+φ&#...
January 24, 2013

Physics
I=const R=R1+R2+R3 +....=
January 24, 2013

science
Use Newton's 3 law: You can get back to your station if you throw your reaction jet away
January 24, 2013

Physics
R1=R(AD)+R(DC)=4+4= 8Ω R2=R(AB)+R(BC)= 4+4= 8Ω 1/R =1/R1 +1/R2= 1/8 + 1/8= 2/8= 1/4 R= 4 Ω
January 24, 2013

physics
Average speed =distance/time= (150+150)/120 =2.5 m/s Average velocity= displacement/time= 0
January 24, 2013

Physics
I=U/(R1+R2) =2.4/(12+8) =1.2 A, U1= I•R1= 1.2•8 = 9.6 V, U2= I •R2=1.2•12=14.4 V.
January 24, 2013

Physics
W=ΔKE= mv²/2 =0.02•150²/2=…
January 24, 2013

Physics
http://www.citycollegiate.com/wave_soundXc.htm
January 24, 2013

Physics
this is the inertial motion
January 24, 2013

physics
T(K) =t℃ +273
January 24, 2013

Physics
d sinθ = 4λ
January 24, 2013

Physics -- please help
y=gt²/2 =9.8•0.19²/2 =4.9•0.19² = … For finding the distance you need v(x) s=v(x)• t
January 24, 2013

Physics
The period is T= 2π•sqrt(m/k) = =2•3.14•sqrt(0.22/12) =0.85 s. It doesn’t depend on „x“
January 24, 2013

science
mv²/2 =mgh h= v²/2g
January 24, 2013

physics
I believe that m= 5.1 X 10^- 3 kg F(electr) + F(spr) = mg, qE + k•ΔL=mg E=( mg- k•ΔL)/q= ={5.1•10⁻³•9.8 – 2.4(0.074-0.059)}/6.6 =… V/m
January 24, 2013

Physics
L(dB) = 10 log₁₀(P₁/P₀)= 10 log₁₀100000= =10•5=50
January 24, 2013

Physics
T=30/50 = 0.6 s. v=s/t= 0.5/15 = 0.033 m/s λ=vT=0.033•0.6= 0.02 m
January 24, 2013

physics Electricity
(a) F=k•q₁•q₂/r²=.... k =9•10⁹ N•m²/C² attraction (b) the law of conservation of charge: q(total) = -20+50 = 30 μC The charge on each sphere is q=15 μC F =k•q²/r² = … repulsion
January 24, 2013

Physics
T₁ =27+273=300 K p₁V₁/T₁= p₂V₂/T₂ T₂ = T₁•p₂V₂/p₁V₁= …. K (!)
January 23, 2013

Physics
v(n) = ℏn/m•r = e²/4•π•ε₀•ℏ•n= =v₁/n=2.19•10⁶/n m/s n=1 v₁=2.19•10⁶ m/s
January 23, 2013

physics
mv²/2=k•q₁q₂/r r = 2k•q₁q₂/mv², where k =9•10⁹ N•m²/C² e =1.6•10⁻¹⁹ C. q₁=2e, q₂=79e m=6.64•10⁻²⁷ kg v=2.6•10⁶ m/s
January 23, 2013

Physics
p1V1 =p2V2 V2=p1V1/p2 d. 0.25 m^3
January 22, 2013

Physics
v(x0) =v(x)=8 m/s v(y0) =0 v(y)=gt=10•3.8=38 m/s v=sqrt{v(x)² +v(y)²} = =sqrt (8²+38²) = 38.8 m/s
January 22, 2013

Physics
F(net) = F-F(res) =(2.06-1.75)•10³=0.31•10³=310 N a=F(net)/m= 310/1300=0.24 m/s² s=at²/2=… v=at = …
January 22, 2013

Physics
W=q•Δφ q= W/Δφ=4.5•10⁻⁴/(300-150)= 3•10⁻⁶C Since this motion takes energy q= - 3•10⁻⁶C
January 22, 2013

physical
v=ωR=2.08•0.25 =… (m/s)
January 22, 2013

Science
http://www.currentresults.com/Weather-Extremes/US/hottest-cities-winter.php
January 22, 2013

Physics
m₁g=kx k= m₁g/x ω=sqrt(k/m₂)=… (rad/s) f=ω/2π=…(Hz)
January 22, 2013

Physics
speed is the magnitude of velocity speed ===scalar velocity === vector
January 22, 2013

physical sciences
when the angle between them is zero
January 22, 2013

science
STP =standard temperature and pressure: T= 273.15 K p=10⁵Pa μ for hydrogen =2 g/mol= 0.002 kg/mol R=8.31 J/mol•K. m=1g=0.001 kg From pV=mRT/μ V= mRT/μp
January 22, 2013

Physics
93 km/h=93000/3600=25.8 m/s Centripetal acceleration is a=v²/R=25.8²/1350 =0.49 m/s² The average acceleration = =Δv/Δt = (v₂-v₁)/Δt Since velocity is vector, vecor Δv can be found as vector difference (taking into account that ...
January 21, 2013

Physics
F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², Solve for R
January 21, 2013

Physics
F =G•m₁•m₂/R² the gravitational constant G =6.67•10⁻¹¹ N•m²/kg², m₁ =10.7 kg Sove for m₂
January 21, 2013

Physics
Earth’s mass is M = 5.97•10²⁴kg, G =6.67•10⁻¹¹ N•m²/kg², R=5 • 6.378•10⁶ = .. (a) mv²/R = G•m •M/R² v=sqrt{ G •M/R) = … (b) T=s/v =3πR/v
January 21, 2013

Physics
mg = G•m •M/R² where R = 6.378•10⁶ m, 100%=12.89% =87.11%. mg₁ =0.8711mg => G•m •M/(R+h)² = 0.8711 G•m •M/R² 0.8711(R+h)² = R² 0.8711 (R² +2Rh+h²) = R² Solve for h
January 21, 2013

Physics
kq₁/x²=kq₂/(6-x)² 2/x²=6/(6-x)² 36-12x+x²=3x² 2x²+12x-36=0 x²+6x-18=0 x = - 3±sqrt(9+18) = = - 3 ± 5.2 If q₁ >0 and q₂>0 x= 2.2 cm (to the right from the left charge (between the charges)) If q...
January 21, 2013

Science
PE->KE mgh=mv²/2 v=sqrt(2gh)
January 21, 2013

physics
C=q/U q= CU
January 21, 2013

physics
A=4πr² => r=A/4π φ=kq/r k =9•10⁹ N•m²/C² φ=516 V, A= 1.01 m^2 q= φr/k=φA/4πk=..
January 20, 2013

Physics
A•B= |A||B| cosα cosα =A•B/ |A||B|= =16/5•5=0.64 α=cos⁻¹α=50.2°
January 20, 2013

physics please please please help me!
neutral atom q=0; if you remove 2 electrons: q= +2•1.6•10⁻¹⁹= +3.2•10⁻¹⁹ C if you add to electrons: q= - 2•1.6•10⁻¹⁹= - 3.2•10⁻¹⁹ C
January 20, 2013

PHYSICS PLEASE HELP!
q₁ = q₂ = 2•e⁻ =- 3.2 •10⁻¹⁹ C k =9•10⁹ N•m²/C² F=k•q₁•q₂/r² = ... repulsive
January 20, 2013

Physics
1/R = 1/2.5 +1/3.5 +1/4 = =0.4+0.2857 +0.25 =0.9357 R=1/0.9357 =1.069 Ohm
January 19, 2013

Physics
1.3 atm =131722.5 Pa p=F/A=4F/πd². d=sqrt(4F/πp)=...
January 19, 2013

thermal physic
T=273+37=310 K KE=3νRT/2 =3•1•8.31•310/2 =3864 J
January 19, 2013

Physics
q= 16 μC = 16•10⁻ ⁶ C, t₁ = 4 s. I=q/t₁=16•10⁻ ⁶/4=4•10⁻ ⁶ A, N=I •t₂/e =4•10⁻ ⁶• 16/1.6•10⁻¹⁹ =4•10¹⁴ .
January 19, 2013

physics
r=0.0205 m α=20⁰, m = 0.00014 kg=1.4•10⁻ ⁴ kg• F(el)=kq₁•q₂/r²=kq²/r², T•sin α =F(el)= kq²/r², T•cosα=mg . T•sin α/ T•cosα= kq²/r²mg, tanα = kq&#...
January 18, 2013

Physics
q₁ = 5 μC =5•10⁻⁶ C, q₂ = - 3 μC = - 3•10⁻⁶ C, r₁ =0.5 m, r₂ = 0.8 m. k =9•10⁹ N•m²/C² E₁=k•q₁/ r₁², (directed ↑) E₂ = k•q₂/ r₂...
January 18, 2013

physics
ΔKE = 9670 – 7540 =2130 eV =2130•1.6•10⁻¹⁹= 3.41•10⁻¹⁶ J Δφ=|φ(A)-φ(B)| = 16 –(-66) = 82 V ΔKE =q• Δφ q =ΔKE/ Δφ =3.41•10⁻¹⁶/82=4.2•...
January 18, 2013

physics
C=q/ Δφ, C=εε₀A/d, q/ Δφ = εε₀A/d, q= εε₀A Δφ /d, where ε =4.1, ε₀=8.85 •10⁻¹² F/m, A=4.4•10⁻⁹m², d=1.64.4•10⁻⁸ m, N=q/e=q/...
January 18, 2013

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