Friday

January 30, 2015

January 30, 2015

Total # Posts: 4,350

**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*

**Phyics help please varify the answer is correct**

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

**physics please need help**

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*

**physics please need help**

f=1/T=1/10⁻³=1000 Hz
*May 31, 2013*

**Phyics please help ms sue**

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*

**Phyics please help ms sue**

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*

**Physic Please Help**

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

**Physic Please Help**

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*

**HELP pyhsic please (critical density)**

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

**Physic problem(2)...Please help**

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*

**Physics**

The angular momentum of the door ‘p’= the change in amgular momentum of the ball Δp. In vector form: Δp⃗ =p₂⃗-p₁⃗ =mv₂⃗-mv₁⃗, for magnitudes Δp =p₂-(-p₁) =mv₂+mv₁= 2mv. p=Mu...
*May 21, 2013*

**Physics**

http://www.jiskha.com/display.cgi?id=1368801920
*May 21, 2013*

**physics**

p=W/A =W/a²=75/0.01=7500 Pa
*May 21, 2013*

**physics**

N=mg => m=N/g = 95/9.8 =9.69 kg
*May 21, 2013*

**physics**

s₁=v²/2a₁=28.8²/2•4=103.7 m. s₁=a₁t₁²/2 => t₁=sqrt(2s₁/a₁) =sqrt(2•103.7/4) =7.2 s. t₂=63.8 s. s₃=v²/2a₃=28.8²/2•1.58=262.5 m s₃=a₃t₃²/2 => t...
*May 21, 2013*

**physics**

s=at²/2=100•25/2=1250 m
*May 21, 2013*

**PHYSICE**

http://teacher.pas.rochester.edu/phy121/lecturenotes/Chapter13/Chapter13.html
*May 21, 2013*

**physical science**

ΔKE =Work mv₂²/2 - mv₁²/2 = W v₂= sqrt{(2/m)•[W+ mv₁²/2]}=…
*May 20, 2013*

**physics**

a=eE/m s=v²/2a
*May 20, 2013*

**Physics**

t=sqrt{2h/g} v=L/t
*May 18, 2013*

**physics**

φ=31⁰π/180⁰ = 0.54 rad. n = 900 rev/min =900/60 =15 rev/s t=φ/ω= φ/2πn=0.54/2π•15=0.006 s v=d/t =0.8/0.006 = 133 m/s
*May 18, 2013*

**physics**

See my answer to a similar question below under related questions.
*May 18, 2013*

**Physics**

t=sqrt{2h/g}
*May 17, 2013*

**physics**

D) {4•100 +4•80} – sqrt(400² +80²) = 72 m
*May 17, 2013*

**physics**

Upward motion: h=v₀t-gt²/2 v= v₀-gt v=0 => t=v₀/g h= v²/2g =30²/2•9.8=45.9 m t=sqrt{2h/g} =sqrt{2•45.9/9.8} = 3.06 s. t(total)=2•t = 2•3.06 =6.12 s.
*May 17, 2013*

**science-physics**

W•0.67 = 183•(1.4-0.67) +107•(2.8-0.67) W={183•0.73+107•2.13}/0.67=540 N
*May 15, 2013*

**Physics**

λ =v/f=330/320 = ... m
*May 15, 2013*

**physics**

Velocity in the stretched string is v = sqrt(TL₀/m) = =sqrt(570•0.92/0.0037) = 376 m/s, λ =2L =2•0.65 = 1.3 m, λ = v/f => f=v/λ =376/1.3=289 Hz.
*May 14, 2013*

**Physics**

mgh = mv²/2 v=sqrt{2gh}
*May 14, 2013*

**Physics helpp**

F-F(gr) = ma a= {F-F(gr)}/m = =(15-10)/15=0.33 m/s² (upward)
*May 14, 2013*

**science physics**

1,2). k =9•10⁹ N•m²/C², q₁=5 C, q₂= - 2.5 C. F=k•q₁•|q₂|)/r² = =9•10⁹•5•2.5/1.75² =3.67•10¹⁰ N (to the right). 3). E=k|q₂|/r² =9•10⁹•2.5/1.75&#...
*May 14, 2013*

**physics**

k =9•10⁹ N•m²/C² F=k•q₁•q₂/r² = =9•10⁹•5•2.5/1.75² =3.67•10¹⁰ N (to the right)
*May 14, 2013*

**physical science**

a=F/m = 14000/2500 =5.6 m/s^2
*May 14, 2013*

**Physics**

m=14 kg F=ma=14 x 1.5 = 21 N
*May 14, 2013*

**Physics to Elena**

(a) The time-averaged Poynting vector is <S> =cε₀E₀²/2. The amplitude of electric field is E=sqrt{2<S>/ cε₀} = =sqrt{2•1.35•10³/3•10⁸•8.85•10⁻¹²} = 1.01•10³ V/m. (b) The ...
*May 14, 2013*

**Physical Science**

KE=mv²/2 m= ρV kinetic energy per unit volume V KE₁ =KE/V= mv²/2V =ρV•v²/2V = ρv²/2
*May 13, 2013*

**Physical Science**

KE=ρv²/2= 1•10³•0.5²/2=125 J
*May 13, 2013*

**physics**

Coulomb’s Law: F=k•q₁•q₂/r² =… F=ma => a=F/m=… r=at²/2 t=sqrt{2r/a)=…
*May 13, 2013*

**physics**

F(BC) =kq²/a² q´(B)=q´(A) =(q+0)/2=q/2, q´´(A) =q´(C) = {q´(A)+c(C)}/2 = 3q/4 F´(BC) =k q´(B)• q´(C)/a² = =(3/8)• kq²/ a²=3•4/8=3.2 = 1.5 N
*May 13, 2013*

**physics/chemistry(kinetic ..gasses)**

<v> =sqrt{3RT/M}=sqrt{3pV/m} => M=mRT/pV =ρRT/p. v=sqrt {γRT/M}. γ=C_p /C_v = (i+2)/i. v=sqrt{9i+2)RT/iM} = sqrt{(i+2)RTp/iρRT}= =sqrt{(i+2)p/iρ}, iρv² - ip = 2p, i=2p/ (ρv² - p) = =2• 1.01325• 10⁵/(1.3&#...
*May 13, 2013*

**Physical Education**

mg=F(buoyant), ρ₁Vg=ρ₂0.64Vg, ρ₁=0.64ρ₂=0.64•806=515.84 kg/m³.
*May 13, 2013*

**physics**

F(BC) =kq²/a². q´(B)=q´(A) =(q+0)/2=q/2, q´´(A) =q´(C) = {q´(A)+c(C)}/2 = 3q/4, F´(BC) =k q´(B)• q´(C)/a² = =(3/8)• kq²/ a²=3•4/8=3.2 = 1.5 N
*May 12, 2013*

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