Monday
December 5, 2016

# Posts by elena

Total # Posts: 4,386

Physics
http://physicsphunhouse.com/physics/ff3.pdf
February 11, 2013

physics
http://farside.ph.utexas.edu/teaching/302l/lectures/node30.html
February 10, 2013

physics
Larger charges have more field lines beginning or ending on them. They allow to estimate the magnitude of the charge => Answer A
February 9, 2013

physics
The 1st law of thermodynamics ΔQ=ΔU+W= ΔU+pΔV For adiabatic process ΔQ=0 => 0=ΔU+pΔV if p=const and ΔV ↑ => ΔU ↓ The internal energy ΔU depends on temperature; and temperature decreases as the kinetic energy ...
February 9, 2013

physics
to throw the wrench in the direction opposite to the satellite and move to the satellite according to the law of conservation of linear momentum
February 9, 2013

arithmetic
a(n) = a₁ +(n-1)d a(6) = a₁ +(6-1)d=12 a(8) = a₁ +(8-1)d=22 a₁ +5d=12 a₁ +7d=22 a₁ = -13 d=5 a(2) = a₁ +(2-1)d= =-13 +5= =-8
February 9, 2013

physics
R+r=100 1/R +1/r =1/24 => (R+r)/Rr=1/24 100/Rr =1/24 rR=2400 Since r=100-R R(100-R)=2400 R²-100R+2400=0 R=40 Ω => r=60 Ω R=60 Ω => r=40Ω
February 9, 2013

physical sciene
v=gt=9.8•3.8=…
February 9, 2013

physics
Mass per unit length m₀ = m/L Velocity in the stretched string is v = sqrt(T/m₀). t=L/v
February 8, 2013

physics
PE=mgh h↓ => PE↓ at the ground PE=0
February 7, 2013

architecture
Describe the differences you observe between the art and architecture of the Early Renaissance (Chapter 8) and that of the High and Late Renaissance. Select an Early Renaissance work of painting, sculpture, and architecture, and compare them to examples from the High or Late ...
February 5, 2013

Physics ASAP!!
Density of wood is ρ₁=600 kg/m³, density of water is ρ₂=1000 kg/m³, m=0.24 kg, M=? The volume of the wooden block is V=m/ρ₁=0.24/600=4•10⁻⁴ m³. Mg+mg=F(buoyancy) Mg+mg= ρ₂•V•g M= ρ₂...
February 4, 2013

Physics
F=ma The downward force on the burning gases from the exhaust is equal to the upward force on the rocket
February 4, 2013

Physics
mv=(m+M)u u=mv/(m+M)=0.045•220/(0.045+5)=1.96 m/s (m+M)u²/2=(m+M)gh h= u²/2g=1.96²/2•9.8=0.196 m
February 3, 2013

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

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

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
January 27, 2013

Physics
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