Sunday

November 23, 2014

November 23, 2014

Total # Posts: 4,334

**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*

**physics capacitor**

C=q/U => U=q/C
*January 18, 2013*

**Physics, help me please?!**

mv²/R = μmg (a) μ=v²/Rg = … (b) v₁=sqrt(μ₁Rg)
*January 18, 2013*

**Physics**

y(x,t)=Asin(kx-wt) Speed dy/dt = - Aωcos(kx-ωt), Max. speed (dy/dt)max =Aω. cos(kx-ωt) =1 => sin(kx-wt)=0 => x=0
*January 18, 2013*

**Physics**

λ=v/f v=λ•f T=m₀•v² = m₀• (λ•f)², T=M•g, m₀• (λ•f)²=Mg, M= m₀• (λf)²/g = =8•10⁻³(1.8•52)²/9.8 =7.15 kg
*January 18, 2013*

**Physics**

T=0.16 s, λ=8 m λ=vT v= λ/T= 8/0.16 =50 m/s f=1/T=1.0.16 =6.25 Hz ω=2πf =… k=2π/ λ=…
*January 18, 2013*

**Physics**

F(ten) = m₀•v² v=sqrt{F(ten)/m₀}, If m₀₂ =2m₀₁ => v₀₁=√2•v₀₂
*January 18, 2013*

**Physics**

b. P=F/A=5000/10=500 Pa
*January 18, 2013*

**Physics**

Q=π•P₁•r₁⁴/8•η• L = π•P₂•r₂⁴/8•η• L P₂=(r₁/r₂)⁴P₁= (100%/70%)⁴• P₁=4.2• P₁. c. The pressure gradient would have to increase...
*January 18, 2013*

**physics**

F=k•q₁•q₁/r², where k =9•10⁹ N•m²/C²
*January 18, 2013*

**Physics**

Q=5 cm³/min = 5•10⁻⁶/60 m³/s d=0.5 mm => r=0.25•10⁻³ m, η=1.5•10⁻³ Pa•s, L =0.05 m ρ=1025 kg/m³ Poiseuille’s law Q=π•P•r⁴/8•η• L. P = 8• Q•η...
*January 18, 2013*

**physics**

N=(q1+q2)/e = (2.4+2.8)•10⁻⁶/1.6•10⁻¹⁹ = =3.25•10¹³
*January 18, 2013*

**Physics**

m=90 kg ρ(He) =0.179 kg/m³ D=11 m => R=5.5 m. ρ(air) =1.29 kg/m³ ( 4πR³/3)•g• ρ(air)= (4 πR³/3 )•g• ρ(He) + (M+m)g, M = (4πR³/3)•{ρ(air) - ρ(He)} – m =….
*January 17, 2013*

**Physics**

sinα =3.2/35 =0.091, α=5.24⁰, tanα=0.092. T•sin α =F(el)=kq₁•q₂/r²=kq²/r², T•cosα=mg . T•sin α/ T•cosα= kq²/r²mg, tanα = kq²/r²mg, q=sqrt{ r²•m•...
*January 17, 2013*

**science**

Aurum Argentum Stannum Hydrargyrum Plumbum Kalium Wolfram Ferrum
*January 17, 2013*

**Chemistry**

a=2.77 Å= 2.77•10⁻⁸ cm. The BCC-cell volume is V=a³=(2.77•10⁻⁸)³ = 2.13•10⁻²³ cm³. Density ρ =8.65g/cm³ per unit cell. Avogadro´s number N₀=6.022•10²³ mol⁻¹...
*January 17, 2013*

**Physics**

v=350 km/h=350000/3600=97.2 m/s c=130 J/kg•K KE -> Q mv²/2 =cmΔT ΔT= v²/2c=97.2²/2• 130= 36.3 K
*January 17, 2013*

**physics**

v=s/t=750/300 =2.5 m/s λ=vT T=λ/v=16.1/2.5 =6.44 s
*January 16, 2013*

**Physics**

sinα =9/20 =0.45 α=sin⁻¹0.45 =26.7⁰
*January 16, 2013*

**physics**

α1 =360⁰-320⁰ =40⁰ F(x) =F1(x)+F2(x) =F1cosα1 + F2cosα2 = =53•cos40 +81•cos13 =40.6+78.9=119.5 N F(y) =F1(y)+F2(y) = - F1sinα1 + F2sinα2 = = - 53•sin40 +81•sin13 = = - 34.07 +18.22 = - 15.85 N F=sqrt{F(x)²+F(y...
*January 16, 2013*

**physics**

α =(360⁰ - 2•100⁰)/2=80⁰ F12=sqrt{F1²+F2²-2•F1•F2•cosα}= =sqrt{400+400-2•20•20•cos80⁰}=25.71 N Direction: F1 is directed along the positive X-axis ,and F2 is 100⁰ measured from the positive X...
*January 16, 2013*

**Physics**

v=200 km/h =200000/3600=55.56 m/s, a=(v-v₀)/t=(55.56-0 )/3=18.52 m/s², a/g= 18.52/9.8= 1.89, F=ma=12000•18.52=2.22•10⁵ N
*January 16, 2013*

**physics**

http://en.wikipedia.org/wiki/Watt P=E/t=1000/10 =100 W
*January 16, 2013*

**science**

ΔPE(A)=ΔKE(C) mgΔh₁= mv(C)²/2 v(C)=sqrt(2gΔh)= =sqrt{2•9.8•(5-2)}=7.67 m/s KE(C) =KE(B) + Δ PE(B) mv(C)²/2 =mv(B)²/2+ mgΔh₂ v(C)² = v(B)² + 2gΔh₂ v(B)=sqrt{ v(C)² -2g(3.2-2)} = … ...
*January 16, 2013*

**Physics**

Q1= rm=330000 x 0.02 = … Q2=cm(T2-T1)=4180 x 0.02 x 15 = ... Q= Q1 +Q2 = …
*January 16, 2013*

**Physics**

1 atm =101300 Paá p=p₀+ρgh= => h=(p-p₀)/ρg = =(108000 -101300)/ 9.8•1024= =0.668 m If ρ₂<ρ₁, h₂>h₁
*January 15, 2013*

**Physics**

k=30 N/m x=0.5 m E=kx²/2
*January 15, 2013*

**Physics**

k=8.98755 × 10^9 =9•10 ⁹N • m^2/C^2. q1=−6 µC, q2 =7 µC, q3 =-5 µC F12=k•q1•q2/r1²=9•10⁹•6•10⁻⁶•7•10⁻⁶/9 =…. (to the right) F13=k•q1•q3/r2²=9...
*January 15, 2013*

**Physics**

m1•v1 + 0= (m1+m2)u u= m1•v1/(m1+m2)
*January 15, 2013*

**Physics**

F=μmg μ=F/mg=99/128•9.8= 0.079
*January 15, 2013*

**physics**

http://en.wikipedia.org/wiki/Refraction http://en.wikipedia.org/wiki/Snell's_law http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html
*January 13, 2013*

**physics**

http://www.chegg.com/homework-help/questions-and-answers/sound-passing-perpendicularly-open-window-dimensions-11-m-x-075-m-sound-intensity-level-98-q3307578
*January 13, 2013*

**Physics**

(a) v₁= (m₁-m₂)v₁₀/(m₁+m₂), v₂={2m₁v₁₀}/(m₁+m₂). (b) u=m₁V₁₀/(m₁+m₂)
*January 13, 2013*

**physics**

s=at²/2 a=2s/t² ma=mgsinα sinα=a/g
*January 13, 2013*

**Physics**

m₁v₁=(m₁+m₂)u u= m₁v₁/(m₁+m₂)
*January 11, 2013*

**Physics**

mv²/(R+h) = GmM/(R+h)² v=sqrt{GM/(R+h)} =…. the gravitational constant G =6.67•10⁻¹¹ N•m²/kg²,
*January 11, 2013*

**Physics**

tanα=0.55/0.4 =1.375. α=54⁰ The distance between the charges d = sqrt(0.4²+0.55²) = 0.68 m The electric field at the disired point is zero => k•q₁/0.68+r)²=k•q₂/r², 0.86r²-1.36r-0.46=0, r ={1.36±sqrt(1.85...
*January 11, 2013*

**physics**

m₁a=m₁g -T m₂a=m₂g-T a(m₁-m₂)=g(m₁+m₂) a =g(m₁+m₂)/(m₁-m₂)= ...
*January 11, 2013*

**physics**

f=1.6 Hz λ=1.5 m v= λf=1.5•1.6=2.4 m/s L=vt/2=2.4•2.9/2=3.48 m.
*January 10, 2013*

**Math PLEASE HELP!!!**

V₁= abc=2•3.5•4 = 28 in³ V₂=A•h=(πD²/4) •h= =3.14•3.2²•3.5/4=28.15 =28.2 in³ V₂ > V₁
*January 10, 2013*

**Math I REALLY NEED HELP!!!!!!!!!**

V= 5 x 11.8 x4.4 =259.6 dm³ =259.6 L
*January 10, 2013*

**Physics THRUST**

a= (v₂²-v₁²)/2h = =(0.5²-20²)/2•100= - 2 m/s² F=m(a-g)= 20000•(2-1.62) =2.76•10⁴ N
*January 10, 2013*

**physics**

KE=ΔPE=412 J mv²/2=mgh v=sqrt(2gh)
*January 10, 2013*

**physics**

PE=mgh=57 x 9.8 x3.7 =...
*January 10, 2013*

**Physics**

e) The new force is the same.
*January 10, 2013*

**Math**

Perform the indicated operations. Reduce the answers to lowest terms.... 1.) 7 3/5 + 2 4/7 = _______________ 2.) 8 5/9 + 15 5/6 =________________ 3.) 14 5/10 + 8 3/5 = ________________ 4.) 5/6 x 3/4 = _____________________ Reduce each fraction to lowest terms. Write improper ...
*January 10, 2013*

**Physics**

a= v²/2s F=ma
*January 10, 2013*

**physics**

Mass per unit length m₀ = m/L, Velocity in the stretched string is v = sqrt(T/m₀) =sqrt(T•L/m), λ=v/f = sqrt(T•L/m)/f, L=f²λ²m/T
*January 10, 2013*

**Physics**

A. KE=eU=1.6•10⁻¹⁹•150 =2.4•10⁻¹⁷ J B. KE=mv²/2 v=sqrt(2•KE/m) C. a= v²/2d D. v=at t=v/a
*January 10, 2013*

**Physics**

v(x)=4•10⁶ m/s, E=150 N/C L= 6 (????) t= L/v(x) F=eE, F=ma, ma=eE a=eE/m where e = 1.6•10⁻¹⁹ C, m=9.1•10⁻³¹ kg, v(y)=at =... v=sqrt{v(x) ²+v(y) ²} =…
*January 10, 2013*

**physics**

Distance = 8+1.2+0.2+4 =13.4 miles Displacement =sqrt{(8-0.2)²+(4-1.2)²} =8.29 miles
*January 10, 2013*

**physic =)**

mv²/2=mgh h= v²/2g=.... v(fin)=v-gt v(fin)=0 t=v/g=..... t(total) =2t v(ground)=v=490 m/s
*January 6, 2013*

**mechanics- physics**

substitute 'a' in s=v₀t - at²/2 and solve for 't'
*January 6, 2013*

**mechanics- physics**

v₀ =5•10⁶ m/s v=2.1•10⁶ m/s s=2•10⁻⁴ = 2•10⁻⁶ m ------------ v= v₀-at a= (v₀-v)/t substitute 'a' in s=v₀t+at²/2 and solve for 't'
*January 6, 2013*

**mechanics_ physics**

PE -> PE(spring) mgh =kx²/2 x=sqrt(2mgh/k)
*January 6, 2013*

**mechanics_ physics**

F=3 N, F(fr) =0.6 N W(F) =F•s=3•1.2 =3.6 J W(fr)=F(fr) •s=0.6•1.2=0.72 J W(total)=W(F) –W(fr)=…
*January 6, 2013*

**physics**

dA/dt = 64πt²=128 πt=128 π•1.5=603.2 cm²/s
*January 4, 2013*

**physics**

R=4t (cm) 6=4t t=1.5 s. A=4πR²=4π(4t)²= =64πt²=64π(1.5)²=452.4 cm²
*January 4, 2013*

**Please help**

18t=30•(4-t) 18t =120 -30t 48t=120 t=120/48 =2.5 18•2.5=45 km
*January 3, 2013*

**Physics...Equilibrium (physics of a clothesline)**

α is the angle that tention T makes with vertical line tan α=5/0.2 =25 α=87.7⁰ 2Tcos α=mg T=mg/2cos α =40•9.8/2•cos87.7⁰ =4884 N
*January 3, 2013*

**physics**

initial velocity and the angle
*January 2, 2013*

**physics**

no, but it's close http://physics.gu.se/~ostlund/ffp/prehistory/Fowlers_greeks_to_galileo.pdf
*January 2, 2013*

**physics**

time
*January 2, 2013*

**physics**

If v=const => a=0 f=F(fr)+mg If f is directed vertically N=0 => F(fr)=μN=0 => f=mg
*January 2, 2013*

**mechanics -physics**

averege v =total dostance/total time = =(15•120 + 18•45)/165 =15.82 m/s
*January 2, 2013*

**Physics**

Doppler shift f₀ = f/(1- v/u) = =880/(1-3.5/343)=889.07 Hz
*January 2, 2013*

**Science 8R - HELP!**

http://wiki.answers.com/Q/What_is_the_difference_between_reflection_and_refraction
*January 2, 2013*

**Anyone Please Help!**

Let t be the time of the motion to east => 300•t=400(7-t) 300t=400•7-400t 700t=400•7 t=4 hours s=300•t=300•4=1200 km
*January 2, 2013*

**physical science**

p1=m1•v1 =2000•5=10000 km•m/s p2=m2•v2=0.009•450=4.05 kg•m/s p1> p2 Impulse F•Δt=m•Δv=linear momentum
*January 2, 2013*

**physical science**

t1=t2=sqrt(2h/g)
*January 2, 2013*

**Physics**

h/s=sinα h=s•sinα PE=KE m•g•h = m•v²/2 v=sqrt(2gh) (b) PE=KE+W(fr) m•g•h = m•v²/2 = +F(fr) •s Solve for ‘v”
*December 30, 2012*

**Physics**

At the top point F(centr) =mg
*December 30, 2012*

**Physics**

Torque= force • distance 150 • (0.5-0.2) = 100 • x x= 150•0.3/100=0.45 m (from the center or at the point 0.95 m mark)
*December 30, 2012*

**science**

a=F/m
*December 27, 2012*

**Physics-mechanics**

mv²/R=GmM/R² v=sqrt(GM/R )=sqrt{6.67•10⁻¹¹•6.42•10²³ /(3.40 •10⁶+175 000)}=3.46•10³ m/s. T=2πR/v=2•3.14•(3.40 •10⁶+175 000)/ 3.46•10³ =6.5•10³ s=1.8 h
*December 27, 2012*

**Physics-mechanics**

density ρ =M/V mg=W=GmM/R² => M= WR²/Gm. V=4πR³/3. ρ =3 WR²/4πR³Gm = =3W/4πRGm = =3•9.8/4•3.14•6.4•10⁶•6.67•10⁻¹¹•1= =5.48•10³ kg/m³
*December 27, 2012*

**science**

http://www.visionlearning.com/library/module_viewer.php?mid=37
*December 26, 2012*

**physics**

t= 2vₒ•sinα/g
*December 23, 2012*

**Physics**

(a)If we place one sheet with its polarization direction 90⁰ to the polarized light then the transmitted intensity will be zero (since I=I₀•cos²α = I₀•cos²90⁰=0). If we use 2 sheets, the 1st sheet rotates by angle α (0<...
*December 21, 2012*

**PHISIC help**

KE -> PE(of elastic deformation) -> KE
*December 21, 2012*

**physics**

F=ma=ma=mv²/2s
*December 21, 2012*

**physics**

http://www.chegg.com/homework-help/questions-and-answers/bars-equilibrium-2-m-long-weighing-92-n-string-pullingdown-bars-attached-04-m-fulcrum-left-q1768975
*December 21, 2012*

**Physics**

m1•v1+0 = m1•u(1x) +m2•u(2x) 0=-m1•u(1y) + m2•u(2y) m1•v1 = m1•u1•cos20⁰+m1•u2•cosα 0= - m1•u1•sin20⁰ +m2•u2•sinα . m1•(v1 -u1•cos20⁰)=m1•u2•cosα, .....(1...
*December 20, 2012*

**PHYSICS**

E=5 x 10^5 N/C m =9.1 x 10^-31 kg e= 1.6 x 10^-19 C ma=eE a= eE/m
*December 20, 2012*

**physics**

v1=a1•t1=5.9•4=23.6 m/s v2= a2•t2 = 4.4•6.5 = 28.6 m/s τ1 =s/v1 =200/23.6=8.47 s. τ2 =s/v2 =200/28.6=6.99 s the total time for the 1st runner 4+8.47 = 12.47 s. fir the 2nd runner 6.5+6.99 = 13.49 s
*December 20, 2012*

**PHISIC help**

As the wavelength decreases, the spreading of the wave at the edges of the aperture also diminishes => the waves will spread out less
*December 20, 2012*

**PHYSICS**

F•Δt=Δp=mΔv=m[v₂-(-v₁)]=m(v₂+v₁) m= F•Δt/ (v₂+v₁)=540•6.9•10⁻³/(42+20) = 0.06 kg
*December 19, 2012*

**Physics**

V=7.5 m/s v=1.52 m/s u=? u(x)=V(x)+v(x)= 0-vsin42⁰= - 1.52•0.67=-1.02 m/s u(y)=V(y)+v(y)= V+vcos42⁰=7.5+1.52•0.0.74=8.63 m/s u=sqrt{u(x)²+ u(y)²}=8.69 m/s tanβ = u(x)/u(y)=1.02/8.63=0.12 β =6.74⁰ (west of north)
*December 19, 2012*

**Physics**

Q₁=Q₂ => cm₁(t₁-t) = cm₂(t-t₂) m₁(t₁-t) = m₂(t-t₂) Solve for ‚t“
*December 17, 2012*

**Physics**

a=(v²-v₀²)/2s=v²/2s F=ma
*December 17, 2012*

**Physics**

P=E/t=F•x/t=F•v
*December 17, 2012*

**physics**

m₁ =0.55 kg,t₁ =96.7℃ c₂=4186 J/kg•℃, m₂=2.19 kg, t₂=4.4℃ t= 7℃ Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c₂m₂(t-t&#...
*December 17, 2012*

**physics**

m₁ =0.55 kg,t₁ =96.7℃ c₂=4186 J/kg•℃, m₂=2.19 kg, t₂=4.4℃ t= 7℃ Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c₂m₂(t-t&#...
*December 17, 2012*

**Pysics**

m₁ =0.55 kg,t₁ =96.7℃ c₂=4186 J/kg•℃, m₂=2.19 kg, t₂=4.4℃ t= 7℃ Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c₂m₂(t-t&#...
*December 17, 2012*

**physics**

efficiency of Otto engine is e= 1 –{V₂/V₁}^(γ-1) γ=(i+2)/i For diatomic gas i=5 =>γ=7/5=1.4 V₁/V₂= CR (compression ratio) e= 1 –{1/CR}^(γ-1)=1-{1/CR} ^0.4 0.331 = 1-{1/CR} ^0.4 Solving for CR, we obtain CR=2.73
*December 17, 2012*

**physics**

CoP=4.5 CoP=Qh/(Qh-Qc)=1/{1-(Qc/Qh)}=4.5 Qc/Qh=0.78 Qc=46.1 cal Qh= Qc/0.78 = 46.1/0.78=59.1 cal
*December 17, 2012*

**physics**

c₁=129 J/kg•℃, m₁ =2.6 kg,t₁ =90℃ c₂=4180 J/kg•℃,m₂=0.21 kg, t₂=23℃ t=? Q₁=c₁m₁(t₁-t) Q₂=c₂m₂(t-t₂) Q₁=Q₂ => c₁m₁(t₁-t) = c&#...
*December 17, 2012*

**physics**

F= mv²/R
*December 17, 2012*

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