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December 20, 2014

Posts by elena


Total # Posts: 4,338

physical
m=ρV=ρπr²h=1950•π•0.051²•0.003=0.048 kg
May 10, 2013

physics
The law of conservation of linear momentum m₁v₁- m₂v₂=(m₁+m₂)u u={m₁v₁- m₂v₂}/(m₁+m₂)
May 10, 2013

physics
F=kx k=F/x W=ΔPE= kx²/2=Fx²/2x= Fx/2=20•0.05/2=0.5 J
May 10, 2013

Physics
F=0 if E = 0 The point is located to the right from the second charge at the distance ‘x’ => kq₁/(X+x)² =kq₂/x² X=1 64/(1+x)² = 16/ x², 3x²-2x-1 =0 , x={2±sqrt(4+12)}/6. x₁=1, x₂=-1/3 (※) Ans: ...
May 9, 2013

physics
Use Right Hand Rule
May 9, 2013

physics
30 = L/v(s) - L/v(p) = =2L/v(p) - L/v(p) = L/v(p), L=30 v(p) = 30•6000=180000 m=180 km
May 9, 2013

physics
1/R +1/R =1/9 2/R =1/9 R=18 Ω
May 9, 2013

physics
R₁=R/4 1/R₀=4/R₁ R₀=R₁/4= R/4•4= R/16
May 9, 2013

physics
I can't understand your given data
May 9, 2013

physics
R₁=R/4 1/R₀=4/R₁ R₀=R₁/4= R/4•4= R/16
May 9, 2013

physical scinsce
F=1000n, F=ma, a=F/m=1000n/10= 100n. a=v²/2s, v²/2s=100n, n= v²/200s=50²/200•10=1.25. The amount of explosive is 1.25•10 =12.5 kg.
May 9, 2013

physics
F=qvBsinα sinα = sin180= 0 => F=0
May 9, 2013

physics
incandescent solids produce a continious spectrum of radistion, excited gases - line spectrum
May 8, 2013

Physics
This is correct solution
May 8, 2013

Physics
ma= Fcos θ –μ(mg-Fsin θ) μ = (Fcos θ -ma)/ (mg-Fsin θ)
May 8, 2013

physics
T=2π•sqrt(L/g) = 2π•sqrt(1.8/3.69) =4.4 s
May 8, 2013

Physics Need quick help please
Number of nuclei N=n•N(A) = (m/μ) • N(A)= =(3 g)•(6.022•10²³ nuclei/mol)/(63 g/mol)=2.87•10²² nuclei The energy required to break all the copper nuclei into their constituent protons and neutrons is (550 MeV ) •(2.87•...
May 8, 2013

Physics Someone help please!
¹₀n+¹º₅B = ⁷₃Li+⁴₂He Δm = m(¹₀n) + m(¹º₅B) – m(⁷₃Li)-m(⁴₂He)= =1.009 + 10.811 – 6.941 – 4.003 = 0.876 u. ΔE=mc²=0.876 •1.66•10⁻&#...
May 8, 2013

Physics to Elena
Number of nuclei N=n•N(A) = (m/μ) • N(A)= =(3 g)•(6.022•10²³ nuclei/mol)/(63 g/mol)=2.87•10²² nuclei The energy required to break all the copper nuclei into their constituent protons and neutrons is (550 MeV ) •(2.87•...
May 8, 2013

Physics to Elena
I believe that the correct answer is 1.58•10¹⁴ J.
May 8, 2013

Physics!
Activity A = λN =ln2•N/T, N=AT/ln2=2.51•10⁵•7.55•10⁶/0.693= =2.73•10¹² nuclei. The mass is m=2.73•10¹²•0.035/6.022•10²³ = =1.6•10⁻¹³ kg
May 8, 2013

Physics please help me out! thank you
v=0.02•3•10⁸=6•10⁶ m/s 1 MegaParsec = 3.26•10⁶ ly Hubble’s Law v=Hd Hubble constant H ~70- 80 km/(s•Mpc) => v= 80d or v=70d d=(6•10⁶/80 000)• 3.26•10⁶ =2.45•10⁸ ly or d=(6•10⁶/...
May 8, 2013

Physics
F=k•q₁•q₂/r² k =8.98755•10⁹ N•m²/C²
May 8, 2013

Physics
Point A: h₁= 22 m, v₁=16 m/s; Point B: h₂= 32 m, r₂= 10 m, v₂=?; Δh₁₂ = h₂-h₁=32-22 = 10 m; Point C: h₃=0, r₃= 20 m, v₃=?; Δh₂₃ = h₂-h₃ = 32 – 0 = 32 m. KE₁+PE...
May 8, 2013

Physics
Number of atoms is N= N(A)•m/μ = =6.022•10²³•0.003/63.5•10⁻³=2.85•10²². Number of nucleons (protons+neutrons) = =2.85•10²²•63=1.8•10²⁴. Energy = 1.8•10²⁴•550&#...
May 7, 2013

Physics Need help please
The decay constant is λ=ln2/T = 0.693/5730 = 1.209•10⁻⁴ yr⁻¹. The fraction of ¹⁴C << ¹²C, => we use the atomic weight of ¹²C to find the number of carbon atoms in 270 g: N= (270/12)•6.022•10&#...
May 7, 2013

physics
R=ρL/A A=πd²/4
May 7, 2013

physics
ρgh=σ/r r = σ/ ρgh=0.0072/1000•9.8•0.2 = = 3.7•10⁻⁵ m= 37μm
May 6, 2013

Physics
η=W/Q =(T₁-T₂)/T₁=1-(T₂/T₁), T₂=T₁(1 – W/Q)= 301(1- 216/2360)=280.7 K
May 5, 2013

Physics
V=V₀sinωt, ω= ω₀=1/sqrt(LC)=1/sqrt(0.015•5•10⁻⁶)= =3652 rad/s. V(t)=40sin3652t. q=CU, q(t) =CV₀sinωt, q(t) =5•10⁻⁶•40sin3652t=2•10⁻⁴sin3652t, I(t) =dq/dt =d(CV₀sinωt)/...
May 5, 2013

physics
h=(u²- v²)/2g v²=u²- 2gh, KE=m•v²/2= m(u²- 2gh)/2, KE=PE => m(u²- 2gh)/2 =mgh, (u²- 2gh)/2= gh, u²=4gh, h= u²/4g.
May 5, 2013

SCIENCE
http://en.wikipedia.org/wiki/Atmospheric_pressure
May 5, 2013

Physics
F=ILBsinα sinα=sin 90⁰=1 => F=ILB =6600•7.65•1.25 =6.31 •10⁴ N F=ma => a=F/m= 6.31 •10⁴/2940 = 21.5 m/s².
May 4, 2013

Finance
A company has identified the following investments as looking promising. Each requires an initial investment of $1.2 million. Which is the best investment? a)a perpetuity that generates a cash flow at the end of year 1 of $100,000, has a growth rate of 1.25%, and a cost of ...
May 4, 2013

Physics 1
λ =2L=2•0.5 = 1 m v= λ•f=1•261.6 = 261.6 m/s v = sqrt(T/m₀)= =sqrt(T•L/m) v²= T•L/m T= v²m/L=261.6²•3.8•10⁻³/0.5=520.10 N
May 3, 2013

physics
α= β => α + β=2 β =120⁰ β=60⁰
May 3, 2013

Physics
v₂=v₁/2, m₂=2m₁. p₁= m₁v₁, p₂=m₂v₂=2m₁•v₁/2= m₁v₁=p₁. KE₁=m₁v₁²/2, KE₂=m₂v₂²/2=2m₁ •v₁²/4•2= m₁v₁...
May 2, 2013

Physics
m₁v =(m₁+m₂)u u= m₁v/(m₁+m₂)=2•22/(2+7)=4.9 m/s
May 2, 2013

Physics
v=gt p=mv=mgt
May 2, 2013

Physics
FΔt=Δp= mΔv
May 2, 2013

Physics
0= MV - mv V=mv/M= 10•420/350 = 12 m/s
May 2, 2013

Physics
KE=PE+W(fr) mv²/2 = mgh +µmgcosα = = mgdsinα +µmgcosα, d= {v²/2 - µ gcosα}/gsinα
May 2, 2013

physics urgent please asnwer it i m begging u
I=j(x)A evB(z) =eE(y) E(y)=vB(z) neAv =j(x)A E(y) = j(x)B(z)/ne Constant of proportionality (Hall coefficient) = 1/ne=m³/C = m³/A•s
May 2, 2013

physics
W=ΔKE =mv₂²/2 - mv₁²/2 =m (v₂²/2 - v₁²/2) m= W/(v₂²/2 - v₁²/2)=…
May 2, 2013

physics
PE = mgh m=PE/gh= 800/6•9.8= 13.61 kg
May 2, 2013

physics
λ=c/f f₁=c/λ₁=3•10⁸/320•10⁻⁹ =9.375•10¹⁴ Hz f₂=c/λ₂=3•10⁸/280•10⁻⁹ =1.071•10¹⁵ Hz
April 30, 2013

Physics
T=273+22=295 K radiant emittance R radiant emittance of the black body R* Stefan-Boltzmann law R*=σT⁴ Stefan-Boltzmann constant σ =5.67•10⁻⁸ W•m⁻²•K⁻⁴ R= =kR*=kσT⁴ E=RAt =kσT⁴At E₁=R...
April 30, 2013

Physics
Q/t=q= k•A•ΔT/Δx ΔT=q•Δx/k•A = = 250•1.7•10⁻³/0.2•1.8=1.18 K
April 30, 2013

Physics
L=ℏ √l(l+1) =√l(l+1)• h/2π l= n-1 => l=0, 1, 2, 3,4. L(max) = √(4•5) • 6.63•10⁻³⁴/2π=4.72•10⁻³⁴ kg•m²/s L(min)= 0
April 30, 2013

Physics Need help plz
The uncertainty in speed Δv = 0.22 m/s Δp•Δx =h/4π Δmv•Δx =h/4π Δv•Δx =h/4πm Δx= h/4π•m •Δv= =6.626•10⁻³⁴/4π•1900•0.22=1.26•10⁻³⁷...
April 30, 2013

Physics
Its incorrect. and you shut up so calles i am awesome
April 30, 2013

Physics
t₁=250/9 – 250/7 = 63.5 s t₂ = 500/8 = 62.5 s Δt=t₁-t₂=63.5 – 62.5 =1 s.
April 30, 2013

physics
mgh= mv²/2 v=sqrt(2gh)
April 29, 2013

physics
Work/time = Power = Force x speed The force is exerted on the bicycle to maintain the constant speed is F=P/v=400/10 = 40 N
April 29, 2013

physics
v=const => net force =0
April 29, 2013

physics
centripetal acceleration a= v²/R= = 4/0.5=8 m/s² centripetal force F= mv²/R= =0.05•4/0.5=0.4 m/s²
April 29, 2013

physics
centripetal acceleration a= mv²/R= =0.05•4/0.5=0.4 m/s²
April 29, 2013

Physics
Pb = lead
April 29, 2013

physics
Please can you tell the numerical value
April 29, 2013

physics
Tsinθ = mv²/R Tcosθ = mg tanθ=v²/Rg
April 29, 2013

physics
ma = Tsinθ mg= Tcosθ a/g =tanθ => a=g• tanθ
April 29, 2013

Physics
L=2.51•10⁻⁶ H x=1.17 m z=? L=μ₀N²A/z N=x/2πr => r= x/2πN => A=πr²=πx²/4π²N² L=μ₀N²A/z= μ₀N²πx²/4π²N²z= = μ₀x²/4z z= &#...
April 28, 2013

chem (boyles and charles law)
p₁ =1.2 atm = 121590 Pa V₁= 1 L=10⁻³ m³ V₂=0.5•10⁻³ m³ p₁V₁=p₂V₂ p₂=p₁V₁/V₂
April 28, 2013

CRC
p₂=p₁T₂/T₁ p₁=675 torr = 89992.35 Pa T ₁=273+28 =301 K T₂ = 273+ 91= 364 K
April 28, 2013

Physics
E₃ = - E₁/n²= - 24.8/9 = - 2.76 eV
April 28, 2013

Physics
covalent bond
April 28, 2013

Physics
T•sin60•L=2450•sin30•0.39L +5000•sin30•L T•sin60=(2450•0.39 +5000)•sin30 T=(2450•0.39 +5000)•sin30/sin60=...
April 28, 2013

physics
mv=(m+M)u u =mv/(m+M), (m+M)u²/2=(m+M)gh. u=sqrt(2gh). mv/(m+M)= sqrt(2gh) v= (m+M)•sqrt(2gh)/m
April 28, 2013

Physical Science
#4
April 28, 2013

chem (boyles and charles law)
T₂=V₂T₁/V₁
April 28, 2013

chem. mix of boyles and charles law
V₂=T₂V₁/T₁ 1 atm = 101325 Pa 1 L = 10⁻³ m³
April 28, 2013

chemistry (charles law)
V₂=T₂V₁/T₁ T₁=303 K T₂=273 K
April 28, 2013

chemistry (charles law)
V₂=T₂V₁/T₁
April 28, 2013

physics
Given data: 1st rod: L₁, T₁, x₁, a => A₁=a²; 2nd rod: L₂, T₂, x₂, d => A₂= πd²/4; Hook’s Law for rods: σ=Eε T/A = E•x/L, 1st rod: T₁/a²= E•x₁/L₁, 2nd rod: 4T&#...
April 28, 2013

Science
m=D•V
April 28, 2013

Physics
m=39.0 kg s=4.5 m, F=135 N, μ=0.3 (a) W(F) = Fs (b) ΔU= W(fr) = μmgs (c) W(N) = 0 (d) W(mg) = 0 (e) KE=W(F) –W(fr) =Fs - μmgs (f) KE=mv²/2 v= sqrt(2•KE/m)
April 28, 2013

physics
The sums of torques respectively the edges of the board are: W•x-400•2 = 0 W• (2-x) -700•2=0 W•x=800 2W-W•x -1400 = 0 2W-800-1400=0 W=1100 N x=800/W =0.73 m
April 28, 2013

physical science
(A)tetrahedral This distorted tetrahedral arrangement is call bent. http://www.ausetute.com.au/shapemol.html
April 28, 2013

physics
h=s•sinα=v•t•sinα=1.5•21•sin30=15.75 m
April 27, 2013

physics
p=sqrt{p(x)²+p(y)²} = = sqrt{(10•9) ² +(20•12)²}=256.32 kg•m/s v= p/(m₁+m₂) =256.32/30 =8.54 m/s
April 27, 2013

physics
k =9•10⁹ N•m²/C² r=0.18 m q₁= 5•10⁻⁹ C q₂ = - 2•10⁻⁹ C PE= k•q₁•q₂/r = ...
April 27, 2013

physics
φ =198t-24t²-2t³ (a) ω=dφ/dt=198 -48t-6t², ω=0 => 198 -48t-6t²=0, 6t²+48t-198=0, t²+8t – 33 =0, t= -4±√(16+33 ) =-4±7, t=-11 (impossible), t=3 s. (b) ε=dω/dt= - 48 -12t. t=3 => ε=-...
April 27, 2013

Physics
F=qE=eE => E=F/e=3•10⁻¹⁵/1.6•10⁻¹⁹= 1.875•10⁴ N E=Δφ/Δx= Δφ/d => Δφ=Ed=1.875•10⁴•0.2=3.75•10³ V
April 27, 2013

Physics
mg=kx x=mg/k=2.35•9.8/1.64•10³=0.014 m
April 26, 2013

Physics
F=k•q₁•q₂/r², k =9•10⁹ N•m²/C², q₂ = F•r²/k•q₁ = 1.8•0.3²/9•10⁹•6•10⁻⁶ = =3•10⁻⁶ C = 3 μC Due to the attraction of the charges q&#...
April 26, 2013

Physics
F=k•q₁•q₂/r²= k•q²/r² q=sqrt{ F•r²/k}=sqrt{7•10⁻⁹•(3.2•10⁻¹⁰)²/9•10⁹}=2.82•10⁻¹⁸C
April 26, 2013

Physics-- please help me finish!!
m₂g=kx k= m₂g/x=0.363•9.8/0.026 = 136.8 N/mþ T=2π•sqrt(m₁/k) = =2π•sqrt(1.4/136.8)=0.64 s
April 26, 2013

physics
L=Iω=mR²ω =0.5•1.45²•1.5 = 0.29 kg•²/s
April 26, 2013

physics
fluorine gas F₂=> μ = 36 g/mol =36•10⁻³ kg/mol, m= 0.076 kg, V=1.5 L = 1.5•10⁻³ m³, t= -37℃ = 236 K, pV=mRT/ μ => p =mRT/ Vμ =0.076•8.31•236/1.5•10⁻³•36•10⁻³= =...
April 26, 2013

Physics SI unit
Newton
April 25, 2013

physics
F₁=mv²/R₁ F₂=mv²/R₂=mv²/2R₁=F₁/2
April 25, 2013

Physics
B=sqrt{B(y)²+B(z)²} = =sqrt{0.5²+0.67²} = 0.836 T, F=qvBsinα, sinα=1, F=qvB=31•10⁻⁶•62•0.836=1.6•10⁻³ N. Vector B makes an angle β with z-axis: tanβ =B(y)/B(z) =0.5/0.67=0.746, β=36.7° ...
April 25, 2013

physics - stopping distance
The reaction time is t =x/v=7.5/10 = 15/20 =22.5/30 = 0.75 s. The reaction distance for v=25 m/s is x=vt=25•0.75 = 18.75 m. The acceleration is a=v²/2s=10²/2•5=20²/2•20=30²/2•45=10 m/s² The breaking distance for v=25 m/s is s= v&#...
April 25, 2013

physics
F=ILB B=F/IL
April 25, 2013

physics
mgh=mv^2/2, v=sqrt(2gh) = ...
April 25, 2013

physics
F=qvB =evB v=F/eB=...
April 25, 2013

physics
engine’s efficiency=A/Q =417/848=0.49 or 49%
April 25, 2013

Physics
A) L=λ/2=v/2f B) L=λ/4=v/4f v is the speed of sound
April 25, 2013

Physics
φ=ω₀t±εt²/2 ω=ω₀±εt ω=2πn ω₀=2πn₀=0 φ=εt²/2 2πn= εt ε=2πn/t φ=εt²/2=2πn t²/2t= πn t=3.14•30•5=...(rad)
April 24, 2013

Physics
mg(H+h)=mv²/2 v = sqrt{2g(H+h)}
April 23, 2013

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