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July 29, 2015

Posts by elena


Total # Posts: 4,370

Physics
drawings????
February 3, 2013

physics
Tsinα=F Tcosα=mg F=mg•tanα T=mg/cosα
February 3, 2013

Physics
E=hf => Electrons jump from third to first orbit
February 3, 2013

Physics
F=0 since F=qvBsinα (α=0)
February 3, 2013

Physics
0.5mgh/t=0.5•10⁵•9.8•30=1.47•10⁷ W N= 1.47•10⁷/100=1.47•10⁵
February 2, 2013

Physcs
The coordinate of dark fringe is y=(2k+1)Lλ/2d. The width of the central bright fringe= the distance between the first dark fringes is 2y₁=2•(2•1+1)Lλ/2d =3 Lλ/d. The distance between the third dark fringes is 2y₃=2•(2•3+1)Lλ...
February 2, 2013

Physics
The speed depends on the refractive index of the substance n n=c/v 1. vacuum: c=3•10⁸ m/s 2. air n= 1.000293 => v= c/n =3•10⁸ /1.000293 =2.999•10⁸ m/s 3. water n=1.333 => v= c/n =3•10⁸ /1.333 =2.25•10⁸ m/s 4. glass n...
February 2, 2013

Physics
Δφ=I₁R₁=I₂R₂=15V
February 2, 2013

Physics
C=q/U=5•10⁻⁶/1.5=3.33•10⁻⁶ F
February 2, 2013

Physics
The third harmonic =>L=3λ/2 =3v/2f= =3•125/2•170=1.103 m
February 2, 2013

Physics Electricity
Potential of the corner point is φ=2•k•q/a. Potential of the center is φ₀=2•k•q•2/a√2=2•k•q•√2/a. Δφ= φ₀ - φ=2•k•q/a(1-√2)= 2•k•q• 0.41/a. ΔKE=Work...
February 1, 2013

physics
Index of reflection (glass) n=c/v, v=nc, s=vt, t=s/v =s/nc, where c=3•10⁸ m/s.
January 30, 2013

Physics
v=28.2 m/s, L=19.5 m. L=v t => t=L/v=... h= gt²/2= ...
January 30, 2013

Physics
(a) KE(rot) =I ω²/2 I=2MR²/5 ω=2π/24•3600 = ...(rad/ s) Earth’s mass is M = 5.97•10²⁴kg, Earth’s radius is R = 6.378•10⁶ m. (b) Linear velocity of the Earth is v=ωr = 2π• 1.496•10¹¹...
January 30, 2013

Physics ~Conservation of Energy~ part 2
1) a) W=mgh b) PE=mgh c) E(toral) = PE = mgh d) KE= PE=mgh e) mv²/2=mgh v=sqrt(2gh) 2) pendelum ... car ???
January 30, 2013

Physics (As Level) 12 Grade
a=v²/2s = 40²/2•860=0.93 m/s² v= v₀-at v=0 t= v₀/a =40/0.93 =43.01 s.
January 30, 2013

Physics (As Level) 12 Grade
a=v²/2s v= v₀-at v=0 t= v₀/a
January 30, 2013

Physics
c=899 J/kg •◦ C, r= 3.97 × 105 J/kg m=2800•0.0136= 38.08 kg E = Q=cm(660.4-26.2) + r m = …
January 30, 2013

Physics
c₁=2090 J/kg ,c₂ = 4186 J/kg •◦ C, c₃ =2010 J/kg •◦ C. λ = 3.33•10^5 J/kg, r = 2.26• 10^6 J/kg. m=0.058 kg Q= c₁m(1)+ λm +c₂m(100) +rm + c₃m(1) = …(J) 1MJ = 10⁶J
January 30, 2013

Physics ~Conservation of Energy~
a) E(total) =KE+PE=5+10 =15 J b) v=sqrt(2•KE/m)=…(m/s) c) KE1=15 -3 =12 J d) v1=sqrt(2•KE1/m)=…(m/s) e) PE= mgh = 3J h=3/mg=3/2.5•9.8=.... (m)
January 30, 2013

Physics ~Work Kinetic Energy~
a) KE₀=0 b) KE= 300 J c) v=sqrt(2•KE/m)=…(m/s) 2) a)W=mgh=450•0.25 = ... J b) KE(fin) =0 c) v=0
January 30, 2013

Physics
Ice: Q= λm + cm(t-0) = λm + cmt Water Q=cm₁(81-t) λ=3.33•10^5 J/kg . m=0.123 kg m₁ = 1.9 kg c = 4186 J/kg •◦ C λm + cmt= c m₁(81-t) Solve for ‚t’
January 30, 2013

physics
v(max) = v =A•ω=A•2πf f = 2Aπ/v
January 30, 2013

Science
Jupiter's gravity may have been too great http://wiki.answers.com/Q/Why_did_the_asteroid_belt_not_form_a_planet
January 29, 2013

mechanics of materials
J=π(D²-d²)/32 =...
January 29, 2013

physic
F = mv^2/r is centripetal force. Velocity in the stretched string is v = sqrt(T/m₀)=sqrt{TL/m}.
January 29, 2013

physics
t= 2vₒ•sinα/g L=vₒ²•sin2α/g,
January 29, 2013

college physics
A=5•10⁻⁶ mm², Silver: k₁= 420 W/m•K, L₁= 0.3 m, Nickel: k₂=91 W/m•K, L₂=0.12 m, T=? q=? Q/t=q=k•A•ΔT/L Resistance of the silver rod: R₁=L₁/k₁A₁ =0.3/420•5•10⁻⁶=...
January 29, 2013

physics
The length and diameter of the platinum wire used in a thermometer are often chosen so that the resistance of the device at around 0 ºC is 100 ohms. Such a sensor is a called a PT100 sensor, and its resistance changes by approximately 0.4 ohms per degree Celsius. Using a ...
January 29, 2013

Physics
m=6.8•10⁻³ kg, q=0.161•10⁻⁶C, A=0.0155 m², α=30°, Q=? Let’s find the projections of the forces acting on the plastic ball: x-projections: Tsinα =F ……. (1) y-projections: Tcosα = mg ……(2) Divide (...
January 29, 2013

Physics
m=6.8•10⁻³ kg, q=0.161•10⁻⁶C, A=0.0155 m², α=30°, Q=? Let’s find the projections of the forces acting on the plastic ball: x-projections: Tsinα =F ……. (1) y-projections: Tcosα = mg ……(2) Divide (...
January 29, 2013

Physics
F=ma=mv²/R m=FR/ v²
January 29, 2013

physics
For the 1st leg of the run: velocity(ave) = displacement/time= 750/20=37.5 m/s For the total trip: velocity(ave) = displacement/time= 0 speed (ave) = distance/time= 1500/45 =33.3 m/s
January 29, 2013

physics
the same as when it started from rest since Δv=at=Ft/m
January 29, 2013

physics
d=sqrt( 4²+5²)=6.4 s=10+4+5=19
January 28, 2013

physics
d=sqrt(5.4²+18²)=18.8 m tan α=18/5.4=3.33 α=73.3° (south from east)
January 28, 2013

physics
Distance (due north) y =d•sin13°= … Distance (due east) x=d•cos13°= …
January 28, 2013

Physical science
F(fr) = μmg
January 28, 2013

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

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