Saturday

February 28, 2015

February 28, 2015

Total # Posts: 4,364

**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*

**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*

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